Depth First Search Interview Questions

Array Depth-First Search Breadth-First Search Matrix Simulation

Rank

#200MediumFrequency: 97.3%

Number of Islands

Array Depth-First Search Breadth-First Search Union-Find Matrix

Rank

#364MediumFrequency: 95.4%

Nested List Weight Sum II

Stack Depth-First Search Breadth-First Search

Rank

#269HardFrequency: 95.2%

Alien Dictionary

Array String Depth-First Search Breadth-First Search Graph Theory Topological Sort Directed Acyclic Graph

Rank

#314MediumFrequency: 93.4%

Binary Tree Vertical Order Traversal

Hash Table Tree Depth-First Search Breadth-First Search Sorting Binary Tree

Rank

#329HardFrequency: 92.5%

Longest Increasing Path in a Matrix

Array Dynamic Programming Depth-First Search Breadth-First Search Graph Theory Topological Sort Memoization Matrix Directed Acyclic Graph

Rank

#124HardFrequency: 90.2%

Binary Tree Maximum Path Sum

Dynamic Programming Tree Depth-First Search Binary Tree DP on Trees

Rank

#339MediumFrequency: 87.9%

Nested List Weight Sum

Depth-First Search Breadth-First Search

Rank

#543EasyFrequency: 86.8%

Diameter of Binary Tree

Rank

#694MediumFrequency: 86.6%

Number of Distinct Islands

Array Hash Table Depth-First Search Breadth-First Search Union-Find Sorting Matrix Hash Function

#10

Rank

#236MediumFrequency: 86.4%

Lowest Common Ancestor of a Binary Tree

Tree Depth-First Search Binary Tree Binary Lifting Lowest Common Ancestor

#11

Rank

#210MediumFrequency: 85.9%

Course Schedule II

Depth-First Search Breadth-First Search Graph Theory Topological Sort

#12

Rank

#199MediumFrequency: 85.4%

Binary Tree Right Side View

Tree Depth-First Search Breadth-First Search Binary Tree

#13

Rank

#2217MediumFrequency: 83.7%

Step-By-Step Directions From a Binary Tree Node to Another

Asked at Databricks

String Tree Depth-First Search Binary Tree Binary Lifting Lowest Common Ancestor

#14

Rank

#1190MediumFrequency: 82.4%

Smallest Common Region

Array Hash Table String Tree Depth-First Search Breadth-First Search Binary Lifting Lowest Common Ancestor

#15

Rank

#207MediumFrequency: 82.3%

Course Schedule

Depth-First Search Breadth-First Search Graph Theory Topological Sort Directed Acyclic Graph

#16

Rank

#230MediumFrequency: 82.3%

Kth Smallest Element in a BST

Tree Depth-First Search Binary Search Tree Binary Tree

#17

Rank

#129MediumFrequency: 78.4%

Sum Root to Leaf Numbers

#18

Rank

#975EasyFrequency: 78%

Range Sum of BST

Tree Depth-First Search Binary Search Tree Binary Tree

#19

Rank

#79MediumFrequency: 78%

Word Search

Array String Backtracking Depth-First Search Matrix

#20

Rank

#3105HardFrequency: 76.8%

Minimum Edge Reversals So Every Node Is Reachable

Dynamic Programming Depth-First Search Breadth-First Search Graph Theory

#21

Rank

#366MediumFrequency: 76.7%

Find Leaves of Binary Tree

#22

Rank

#854HardFrequency: 72.8%

Making A Large Island

Array Depth-First Search Breadth-First Search Union-Find Matrix

#23

Rank

#2905HardFrequency: 71.9%

Count Paths That Can Form a Palindrome in a Tree

Hash Table Bit Manipulation Tree Depth-First Search

#24

Rank

#156MediumFrequency: 70.9%

Binary Tree Upside Down

#25

Rank

#133MediumFrequency: 70.5%

Clone Graph

Hash Table Depth-First Search Breadth-First Search Graph Theory

#26

Rank

#399MediumFrequency: 70.2%

Evaluate Division

Array String Depth-First Search Breadth-First Search Union-Find Graph Theory Shortest Path Bellman–Ford Algorithm Floyd–Warshall Algorithm

#27

Rank

#3875HardFrequency: 69.8%

Maximum Good Subtree Score

Array Dynamic Programming Bit Manipulation Tree Depth-First Search Bitmask

#28

Rank

#1029HardFrequency: 69.1%

Vertical Order Traversal of a Binary Tree

Hash Table Tree Depth-First Search Breadth-First Search Sorting Binary Tree

#29

Rank

#235MediumFrequency: 66.5%

Lowest Common Ancestor of a Binary Search Tree

Tree Depth-First Search Binary Search Tree Binary Tree Binary Lifting Lowest Common Ancestor

#30

Rank

#960HardFrequency: 66.4%

Minimize Malware Spread

Array Hash Table Depth-First Search Breadth-First Search Union-Find Graph Theory

#31

Rank

#893MediumFrequency: 65.7%

All Nodes Distance K in Binary Tree

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree

#32

Rank

#385MediumFrequency: 65.5%

Mini Parser

String Stack Depth-First Search

#33

Rank

#803MediumFrequency: 65.5%

Cheapest Flights Within K Stops

Dynamic Programming Depth-First Search Breadth-First Search Graph Theory Heap (Priority Queue)Shortest Path

#34

Rank

#104EasyFrequency: 65%

Maximum Depth of Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#35

Rank

#3863MediumFrequency: 64.9%

Power Grid Maintenance

Array Hash Table Depth-First Search Breadth-First Search Union-Find Graph Theory Heap (Priority Queue)Ordered Set

#36

Rank

#758MediumFrequency: 63.7%

Convert Binary Search Tree to Sorted Doubly Linked List

Linked List Stack Tree Depth-First Search Binary Search Tree Binary Tree Doubly-Linked List

#37

Rank

#101EasyFrequency: 63.4%

Symmetric Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#38

Rank

#297HardFrequency: 63.4%

Serialize and Deserialize Binary Tree

String Tree Depth-First Search Breadth-First Search Design Binary Tree

#39

Rank

#2584MediumFrequency: 62.5%

Number of Nodes With Value One

Array Tree Depth-First Search Breadth-First Search Binary Tree

#40

Rank

#3977HardFrequency: 62.5%

Count Non Adjacent Subsets in a Rooted Tree

#41

Rank

#270EasyFrequency: 61.8%

Closest Binary Search Tree Value

Binary Search Tree Depth-First Search Binary Search Tree Binary Tree

#42

Rank

#971MediumFrequency: 61.8%

Shortest Bridge

Array Depth-First Search Breadth-First Search Matrix

#43

Rank

#272HardFrequency: 61.6%

Closest Binary Search Tree Value II

Two Pointers Stack Tree Depth-First Search Binary Search Tree Heap (Priority Queue)Binary Tree

#44

Rank

#721MediumFrequency: 61.4%

Accounts Merge

Array Hash Table String Depth-First Search Breadth-First Search Union-Find Sorting

#45

Rank

#743MediumFrequency: 61.1%

Closest Leaf in a Binary Tree

Asked at Databricks

Tree Depth-First Search Breadth-First Search Binary Tree

#46

Rank

#671EasyFrequency: 60.7%

Second Minimum Node In a Binary Tree

#47

Rank

#2175MediumFrequency: 59.9%

Count Nodes With the Highest Score

Array Tree Depth-First Search Binary Tree DP on Trees

#48

Rank

#417MediumFrequency: 59.8%

Pacific Atlantic Water Flow

Array Depth-First Search Breadth-First Search Matrix

#49

Rank

#695MediumFrequency: 59.3%

Max Area of Island

Array Depth-First Search Breadth-First Search Union-Find Matrix

#50

Rank

#490MediumFrequency: 57.5%

The Maze

Array Depth-First Search Breadth-First Search Matrix

#51

Rank

#2583HardFrequency: 57.5%

Divide Nodes Into the Maximum Number of Groups

Depth-First Search Breadth-First Search Union-Find Graph Theory

#52

Rank

#1308MediumFrequency: 57%

Smallest String With Swaps

Asked at PayPal

Array Hash Table String Depth-First Search Breadth-First Search Union-Find Sorting

#53

Rank

#3497HardFrequency: 55.1%

Find the Last Marked Nodes in Tree

Tree Depth-First Search

#54

Rank

#922MediumFrequency: 54.4%

Possible Bipartition

Depth-First Search Breadth-First Search Union-Find Graph Theory Graph Coloring Bipartite Graph

#55

Rank

#211MediumFrequency: 54.4%

Design Add and Search Words Data Structure

String Depth-First Search Design Trie

#56

Rank

#3613MediumFrequency: 54.1%

Maximize Amount After Two Days of Conversions

Array String Depth-First Search Breadth-First Search Graph Theory

#57

Rank

#505MediumFrequency: 54.1%

The Maze II

Array Depth-First Search Breadth-First Search Graph Theory Heap (Priority Queue)Matrix Shortest Path Dijkstra's Algorithm Heuristic Search A* Search

#58

Rank

#1431MediumFrequency: 53.4%

All Ancestors of a Node in a Directed Acyclic Graph

Depth-First Search Breadth-First Search Graph Theory Topological Sort Directed Acyclic Graph

#59

Rank

#472HardFrequency: 53%

Concatenated Words

Array String Dynamic Programming Depth-First Search Trie Sorting

#60

Rank

#733EasyFrequency: 53%

Flood Fill

Array Depth-First Search Breadth-First Search Matrix

#61

Rank

#2461MediumFrequency: 52.9%

Amount of Time for Binary Tree to Be Infected

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree

#62

Rank

#662MediumFrequency: 52.9%

Maximum Width of Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#63

Rank

#1300HardFrequency: 52.9%

Critical Connections in a Network

Depth-First Search Graph Theory Biconnected Component Bridge (Graph)

#64

Rank

#98MediumFrequency: 52.8%

Validate Binary Search Tree

Tree Depth-First Search Binary Search Tree Binary Tree

#65

Rank

#2347MediumFrequency: 52.7%

Count Nodes Equal to Average of Subtree

#66

Rank

#337MediumFrequency: 52.1%

House Robber III

Dynamic Programming Tree Depth-First Search Binary Tree DP on Trees

#67

Rank

#341MediumFrequency: 51%

Flatten Nested List Iterator

Stack Tree Depth-First Search Design Queue Iterator

#68

Rank

#565MediumFrequency: 51%

Array Nesting

Array Depth-First Search

#69

Rank

#547MediumFrequency: 50.7%

Number of Provinces

Depth-First Search Breadth-First Search Union-Find Graph Theory

#70

Rank

#1780MediumFrequency: 50.6%

Lowest Common Ancestor of a Binary Tree II

Tree Depth-First Search Binary Tree Binary Lifting Lowest Common Ancestor

#71

Rank

#881MediumFrequency: 50.3%

Loud and Rich

Asked at PayPal

Array Depth-First Search Graph Theory Topological Sort Directed Acyclic Graph

#72

Rank

#110EasyFrequency: 50%

Balanced Binary Tree

#73

Rank

#999MediumFrequency: 49.9%

Regions Cut By Slashes

Array Hash Table Depth-First Search Breadth-First Search Union-Find Matrix Planar Graph

#74

Rank

#545MediumFrequency: 49.3%

Boundary of Binary Tree

#75

Rank

#116MediumFrequency: 48.8%

Populating Next Right Pointers in Each Node

Linked List Tree Depth-First Search Breadth-First Search Binary Tree

#76

Rank

#617EasyFrequency: 48.8%

Merge Two Binary Trees

Tree Depth-First Search Breadth-First Search Binary Tree

#77

Rank

#257EasyFrequency: 48.7%

Binary Tree Paths

String Backtracking Tree Depth-First Search Binary Tree

#78

Rank

#100EasyFrequency: 48.1%

Same Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#79

Rank

#365MediumFrequency: 48%

Water and Jug Problem

Math Depth-First Search Breadth-First Search Bézout's Lemma Euclidean Algorithm Greatest Common Divisor Extended Euclidean Algorithm

#80

Rank

#419MediumFrequency: 47.5%

Battleships in a Board

Array Depth-First Search Matrix

#81

Rank

#536MediumFrequency: 47.5%

Construct Binary Tree from String

String Stack Tree Depth-First Search Binary Tree

#82

Rank

#690MediumFrequency: 47.5%

Employee Importance

Array Hash Table Tree Depth-First Search Breadth-First Search

#83

Rank

#1558MediumFrequency: 47.5%

Course Schedule IV

Depth-First Search Breadth-First Search Graph Theory Topological Sort

#84

Rank

#1643MediumFrequency: 47.5%

Number of Nodes in the Sub-Tree With the Same Label

Hash Table Tree Depth-First Search Breadth-First Search Counting DP on Trees

#85

Rank

#2065HardFrequency: 47.5%

Check for Contradictions in Equations

Array String Depth-First Search Union-Find Graph Theory

#86

Rank

#130MediumFrequency: 46.9%

Surrounded Regions

Array Depth-First Search Breadth-First Search Union-Find Matrix

#87

Rank

#2364HardFrequency: 44.8%

Longest Path With Different Adjacent Characters

Array String Tree Depth-First Search Graph Theory Topological Sort

#88

Rank

#261MediumFrequency: 44.7%

Graph Valid Tree

Depth-First Search Breadth-First Search Union-Find Graph Theory

#89

Rank

#515MediumFrequency: 44.7%

Find Largest Value in Each Tree Row

Tree Depth-First Search Breadth-First Search Binary Tree

#90

Rank

#529MediumFrequency: 44.4%

Minesweeper

Array Depth-First Search Breadth-First Search Matrix

#91

Rank

#94EasyFrequency: 44.2%

Binary Tree Inorder Traversal

Stack Tree Depth-First Search Binary Tree

#92

Rank

#1576MediumFrequency: 44%

Reorder Routes to Make All Paths Lead to the City Zero

Depth-First Search Breadth-First Search Graph Theory

#93

Rank

#298MediumFrequency: 44%

Binary Tree Longest Consecutive Sequence

#94

Rank

#113MediumFrequency: 43.2%

Path Sum II

Backtracking Tree Depth-First Search Binary Tree

#95

Rank

#332HardFrequency: 43.2%

Reconstruct Itinerary

Array String Depth-First Search Graph Theory Sorting Heap (Priority Queue)Eulerian Circuit Eulerian Path Semi-Eulerian Graph

#96

Rank

#226EasyFrequency: 43%

Invert Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#97

Rank

#3825MediumFrequency: 42.7%

Apply Substitutions

Array Hash Table String Depth-First Search Breadth-First Search Graph Theory Topological Sort

#98

Rank

#323MediumFrequency: 42.2%

Number of Connected Components in an Undirected Graph

Depth-First Search Breadth-First Search Union-Find Graph Theory

#99

Rank

#744MediumFrequency: 41.2%

Network Delay Time

Depth-First Search Breadth-First Search Graph Theory Heap (Priority Queue)Shortest Path Dijkstra's Algorithm

#100

Rank

#1442MediumFrequency: 40.9%

Number of Operations to Make Network Connected

Asked at PayPal

Depth-First Search Breadth-First Search Union-Find Graph Theory

#101

Rank

#1554MediumFrequency: 40.7%

Minimum Time to Collect All Apples in a Tree

Hash Table Tree Depth-First Search Breadth-First Search DP on Trees

#102

Rank

#112EasyFrequency: 40.5%

Path Sum

Tree Depth-First Search Breadth-First Search Binary Tree

#103

Rank

#114MediumFrequency: 40.5%

Flatten Binary Tree to Linked List

Linked List Stack Tree Depth-First Search Binary Tree

#104

Rank

#1207MediumFrequency: 40.2%

Delete Nodes And Return Forest

Array Hash Table Tree Depth-First Search Binary Tree

#105

Rank

#117MediumFrequency: 40%

Populating Next Right Pointers in Each Node II

Linked List Tree Depth-First Search Breadth-First Search Binary Tree

#106

Rank

#794HardFrequency: 40%

Swim in Rising Water

Array Binary Search Depth-First Search Breadth-First Search Union-Find Minimax Heap (Priority Queue)Matrix Dijkstra's Algorithm

#107

Rank

#1931MediumFrequency: 40%

Shortest Path in a Hidden Grid

Array Depth-First Search Breadth-First Search Matrix Interactive

#108

Rank

#99MediumFrequency: 39.4%

Recover Binary Search Tree

Tree Depth-First Search Binary Search Tree Binary Tree

#109

Rank

#871MediumFrequency: 39.4%

Keys and Rooms

Depth-First Search Breadth-First Search Graph Theory

#110

Rank

#765HardFrequency: 39.4%

Serialize and Deserialize N-ary Tree

String Tree Depth-First Search Breadth-First Search

#111

Rank

#642HardFrequency: 39.1%

Design Search Autocomplete System

String Depth-First Search Design Trie Sorting Heap (Priority Queue)Data Stream

#112

Rank

#1653MediumFrequency: 39.1%

Number of Good Leaf Nodes Pairs

#113

Rank

#1177MediumFrequency: 39.1%

Tree Diameter

Tree Depth-First Search Breadth-First Search Graph Theory Topological Sort DP on Trees

#114

Rank

#437MediumFrequency: 39.1%

Path Sum III

#115

Rank

#582MediumFrequency: 39.1%

Kill Process

Array Hash Table Tree Depth-First Search Breadth-First Search

#116

Rank

#896MediumFrequency: 38.5%

Smallest Subtree with all the Deepest Nodes

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree Binary Lifting Lowest Common Ancestor DP on Trees

#117

Rank

#2564MediumFrequency: 37.9%

Most Profitable Path in a Tree

Array Tree Depth-First Search Breadth-First Search Graph Theory

#118

Rank

#1753MediumFrequency: 37.3%

Path With Minimum Effort

Array Binary Search Depth-First Search Breadth-First Search Union-Find Heap (Priority Queue)Matrix Dijkstra's Algorithm

#119

Rank

#2206MediumFrequency: 36.9%

Detonate the Maximum Bombs

Array Math Depth-First Search Breadth-First Search Graph Theory Geometry

#120

Rank

#653EasyFrequency: 35.7%

Two Sum IV - Input is a BST

Hash Table Two Pointers Tree Depth-First Search Breadth-First Search Binary Search Tree Binary Tree

#121

Rank

#1544MediumFrequency: 35.7%

Count Good Nodes in Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#122

Rank

#1665MediumFrequency: 35.6%

Diameter of N-Ary Tree

Tree Depth-First Search DP on Trees

#123

Rank

#820MediumFrequency: 35.1%

Find Eventual Safe States

Depth-First Search Breadth-First Search Graph Theory Topological Sort Kosaraju's Algorithm Tarjan's SCC Algorithm

#124

Rank

#1008HardFrequency: 35.1%

Binary Tree Cameras

Dynamic Programming Tree Depth-First Search Binary Tree DP on Trees

#125

Rank

#1475HardFrequency: 35.1%

Maximum Sum BST in Binary Tree

Dynamic Programming Tree Depth-First Search Binary Search Tree Binary Tree DP on Trees

#126

Rank

#1428MediumFrequency: 34.3%

Jump Game III

Array Depth-First Search Breadth-First Search

#127

Rank

#801MediumFrequency: 34.2%

Is Graph Bipartite?

Depth-First Search Breadth-First Search Union-Find Graph Theory Graph Coloring Bipartite Graph

#128

Rank

#2035MediumFrequency: 34.2%

Count Sub Islands

Array Depth-First Search Breadth-First Search Union-Find Matrix

#129

Rank

#869HardFrequency: 34.2%

Similar String Groups

Array Hash Table String Depth-First Search Breadth-First Search Union-Find

#130

Rank

#1218MediumFrequency: 34%

Lowest Common Ancestor of Deepest Leaves

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree Binary Lifting Lowest Common Ancestor DP on Trees

#131

Rank

#684MediumFrequency: 33.7%

Redundant Connection

Depth-First Search Breadth-First Search Union-Find Graph Theory

#132

Rank

#463EasyFrequency: 33.3%

Island Perimeter

Array Depth-First Search Breadth-First Search Matrix

#133

Rank

#1380MediumFrequency: 33.3%

Number of Closed Islands

Array Depth-First Search Breadth-First Search Union-Find Matrix

#134

Rank

#1347HardFrequency: 33.3%

Distance to a Cycle in Undirected Graph

Depth-First Search Breadth-First Search Graph Theory Topological Sort

#135

Rank

#1254MediumFrequency: 33%

Deepest Leaves Sum

Tree Depth-First Search Breadth-First Search Binary Tree

#136

Rank

#2121EasyFrequency: 32.8%

Find if Path Exists in Graph

Depth-First Search Breadth-First Search Union-Find Graph Theory

#137

Rank

#572EasyFrequency: 31.9%

Subtree of Another Tree

Tree Depth-First Search String Matching Binary Tree Hash Function

#138

Rank

#863HardFrequency: 31.8%

Sum of Distances in Tree

Dynamic Programming Tree Depth-First Search Graph Theory DP on Trees

#139

Rank

#1114MediumFrequency: 31.3%

Binary Search Tree to Greater Sum Tree

Tree Depth-First Search Binary Search Tree Binary Tree

#140

Rank

#3058HardFrequency: 31.3%

Maximum Number of K-Divisible Components

Tree Depth-First Search

#141

Rank

#1492MediumFrequency: 31.3%

Time Needed to Inform All Employees

#142

Rank

#2545HardFrequency: 31.1%

Height of Binary Tree After Subtree Removal Queries

Array Tree Depth-First Search Breadth-First Search Binary Tree

#143

Rank

#1465MediumFrequency: 31.1%

Maximum Product of Splitted Binary Tree

#144

Rank

#310MediumFrequency: 30.4%

Minimum Height Trees

Depth-First Search Breadth-First Search Graph Theory Topological Sort

#145

Rank

#652MediumFrequency: 30.4%

Find Duplicate Subtrees

Hash Table Tree Depth-First Search Binary Tree

#146

Rank

#766MediumFrequency: 30.2%

Flatten a Multilevel Doubly Linked List

Linked List Depth-First Search Doubly-Linked List

#147

Rank

#513MediumFrequency: 29.3%

Find Bottom Left Tree Value

Tree Depth-First Search Breadth-First Search Binary Tree

#148

Rank

#672MediumFrequency: 29.3%

Bulb Switcher II

Math Bit Manipulation Depth-First Search Breadth-First Search

#149

Rank

#2246HardFrequency: 29.3%

Maximum Employees to Be Invited to a Meeting

Array Dynamic Programming Depth-First Search Graph Theory Topological Sort Kosaraju's Algorithm Tarjan's SCC Algorithm

#150

Rank

#2568MediumFrequency: 29.3%

Minimum Fuel Cost to Report to the Capital

Tree Depth-First Search Breadth-First Search Graph Theory

#151

Rank

#4151HardFrequency: 29.3%

Maximum Subgraph Score in a Tree

#152

Rank

#984MediumFrequency: 29.1%

Most Stones Removed with Same Row or Column

Hash Table Depth-First Search Union-Find Graph Theory Bipartite Graph

#153

Rank

#530EasyFrequency: 28.9%

Minimum Absolute Difference in BST

Tree Depth-First Search Breadth-First Search Binary Search Tree Binary Tree

#154

Rank

#1350MediumFrequency: 28.9%

Remove Sub-Folders from the Filesystem

Array String Depth-First Search Trie

#155

Rank

#1116MediumFrequency: 28.1%

Maximum Level Sum of a Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#156

Rank

#386MediumFrequency: 28.1%

Lexicographical Numbers

Depth-First Search Trie

#157

Rank

#404EasyFrequency: 28.1%

Sum of Left Leaves

Tree Depth-First Search Breadth-First Search Binary Tree

#158

Rank

#1093HardFrequency: 27.8%

Recover a Tree From Preorder Traversal

String Tree Depth-First Search Binary Tree

#159

Rank

#1285MediumFrequency: 27.8%

Balance a Binary Search Tree

Divide and Conquer Greedy Tree Depth-First Search Binary Search Tree Binary Tree

#160

Rank

#2403MediumFrequency: 27.8%

Count Unreachable Pairs of Nodes in an Undirected Graph

Depth-First Search Breadth-First Search Union-Find Graph Theory

#161

Rank

#3675HardFrequency: 27.8%

Maximize Sum of Weights after Edge Removals

Dynamic Programming Tree Depth-First Search Sorting

#162

Rank

#285MediumFrequency: 27.3%

Inorder Successor in BST

Tree Depth-First Search Binary Search Tree Binary Tree

#163

Rank

#333MediumFrequency: 27.3%

Largest BST Subtree

Dynamic Programming Tree Depth-First Search Binary Search Tree Binary Tree DP on Trees

#164

Rank

#1201MediumFrequency: 27.3%

Delete Tree Nodes

Array Tree Depth-First Search Breadth-First Search DP on Trees

#165

Rank

#1609EasyFrequency: 27.3%

Find All The Lonely Nodes

Tree Depth-First Search Breadth-First Search Binary Tree

#166

Rank

#3304MediumFrequency: 27.3%

Maximum Subtree of the Same Color

#167

Rank

#3467MediumFrequency: 27.3%

Find the Level of Tree with Minimum Sum

Tree Depth-First Search Breadth-First Search Binary Tree

#168

Rank

#3386HardFrequency: 27.3%

Find Edges in Shortest Paths

Depth-First Search Breadth-First Search Graph Theory Heap (Priority Queue)Shortest Path

#169

Rank

#1296HardFrequency: 27.2%

Kth Ancestor of a Tree Node

Binary Search Dynamic Programming Bit Manipulation Tree Depth-First Search Breadth-First Search Design Binary Lifting

#170

Rank

#144EasyFrequency: 27.2%

Binary Tree Preorder Traversal

Stack Tree Depth-First Search Binary Tree

#171

Rank

#1073MediumFrequency: 27.2%

Number of Enclaves

Array Depth-First Search Breadth-First Search Union-Find Matrix

#172

Rank

#1498EasyFrequency: 26.7%

Find a Corresponding Node of a Binary Tree in a Clone of That Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#173

Rank

#1959MediumFrequency: 26.7%

Minimum Path Cost in a Hidden Grid

Array Depth-First Search Breadth-First Search Graph Theory Heap (Priority Queue)Matrix Interactive Shortest Path

#174

Rank

#508MediumFrequency: 26.5%

Most Frequent Subtree Sum

Hash Table Tree Depth-First Search Binary Tree DP on Trees

#175

Rank

#1092MediumFrequency: 26.5%

Maximum Difference Between Node and Ancestor

#176

Rank

#1624MediumFrequency: 26.5%

Clone Binary Tree With Random Pointer

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree

#177

Rank

#1816MediumFrequency: 26.5%

Lowest Common Ancestor of a Binary Tree IV

Hash Table Tree Depth-First Search Binary Tree Binary Lifting Lowest Common Ancestor

#178

Rank

#2677MediumFrequency: 26.5%

Cousins in Binary Tree II

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree

#179

Rank

#388MediumFrequency: 26.3%

Longest Absolute File Path

String Stack Depth-First Search

#180

Rank

#501EasyFrequency: 25.4%

Find Mode in Binary Search Tree

Tree Depth-First Search Binary Search Tree Binary Tree

#181

Rank

#1099MediumFrequency: 25.4%

Path With Maximum Minimum Value

Array Binary Search Depth-First Search Breadth-First Search Union-Find Heap (Priority Queue)Matrix Dijkstra's Algorithm

#182

Rank

#3439HardFrequency: 25.3%

Find Minimum Diameter After Merging Two Trees

Tree Depth-First Search Breadth-First Search Graph Theory

#183

Rank

#449MediumFrequency: 25.1%

Serialize and Deserialize BST

String Tree Depth-First Search Breadth-First Search Design Binary Search Tree Binary Tree

#184

Rank

#538MediumFrequency: 25.1%

Convert BST to Greater Tree

Tree Depth-First Search Binary Search Tree Binary Tree

#185

Rank

#711HardFrequency: 25.1%

Number of Distinct Islands II

Array Hash Table Depth-First Search Breadth-First Search Union-Find Sorting Matrix Hash Function

#186

Rank

#813MediumFrequency: 25.1%

All Paths From Source to Target

Backtracking Depth-First Search Breadth-First Search Graph Theory Directed Acyclic Graph

#187

Rank

#1079EasyFrequency: 25.1%

Sum of Root To Leaf Binary Numbers

#188

Rank

#1243MediumFrequency: 25.1%

Sum of Nodes with Even-Valued Grandparent

Tree Depth-First Search Breadth-First Search Binary Tree

#189

Rank

#637EasyFrequency: 25.1%

Average of Levels in Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#190

Rank

#1275MediumFrequency: 25.1%

Validate Binary Tree Nodes

Tree Depth-First Search Breadth-First Search Union-Find Graph Theory Binary Tree

#191

Rank

#1368MediumFrequency: 25.1%

Web Crawler Multithreaded

Depth-First Search Breadth-First Search Concurrency

#192

Rank

#111EasyFrequency: 25%

Minimum Depth of Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#193

Rank

#3752MediumFrequency: 24.6%

Unit Conversion II

Array Math Depth-First Search Breadth-First Search Graph Theory

#194

Rank

#1396MediumFrequency: 24.4%

Count Servers that Communicate

Array Depth-First Search Breadth-First Search Union-Find Matrix Counting

#195

Rank

#1840MediumFrequency: 24.4%

Minimize Hamming Distance After Swap Operations

Array Depth-First Search Union-Find

#196

Rank

#2213HardFrequency: 24.4%

Find All People With Secret

Depth-First Search Breadth-First Search Union-Find Graph Theory Sorting

#197

Rank

#1150MediumFrequency: 23.6%

Two Sum BSTs

Two Pointers Binary Search Stack Tree Depth-First Search Binary Search Tree Binary Tree

#198

Rank

#1427MediumFrequency: 23.6%

All Elements in Two Binary Search Trees

Tree Depth-First Search Binary Search Tree Sorting Binary Tree

#199

Rank

#1883MediumFrequency: 23.6%

Find Distance in a Binary Tree

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree Binary Lifting Lowest Common Ancestor

#200

Rank

#754HardFrequency: 23.3%

Cracking the Safe

String Depth-First Search Graph Theory Eulerian Circuit Eulerian Path Eulerian Graph

#201

Rank

#988MediumFrequency: 23.3%

Flip Equivalent Binary Trees

#202

Rank

#2101HardFrequency: 23.3%

Last Day Where You Can Still Cross

Array Binary Search Depth-First Search Breadth-First Search Union-Find Matrix

#203

Rank

#1030MediumFrequency: 23.3%

Smallest String Starting From Leaf

String Backtracking Tree Depth-First Search Binary Tree

#204

Rank

#3603HardFrequency: 23.3%

Check if DFS Strings Are Palindromes

Array Hash Table String Tree Depth-First Search Hash Function

#205

Rank

#676MediumFrequency: 22.1%

Implement Magic Dictionary

Hash Table String Depth-First Search Design Trie

#206

Rank

#737MediumFrequency: 22%

Sentence Similarity II

Array Hash Table String Depth-First Search Breadth-First Search Union-Find

#207

Rank

#606MediumFrequency: 21.9%

Construct String from Binary Tree

String Tree Depth-First Search Binary Tree

#208

Rank

#1021MediumFrequency: 21.9%

Distribute Coins in Binary Tree

#209

Rank

#1157MediumFrequency: 21.9%

Insufficient Nodes in Root to Leaf Paths

#210

Rank

#1450MediumFrequency: 21.9%

Delete Leaves With a Given Value

#211

Rank

#2400HardFrequency: 21.9%

Minimum Score After Removals on a Tree

Array Bit Manipulation Tree Depth-First Search

#212

Rank

#3218HardFrequency: 21.9%

Find Number of Coins to Place in Tree Nodes

Dynamic Programming Tree Depth-First Search Sorting Heap (Priority Queue)DP on Trees

#213

Rank

#4072HardFrequency: 21.9%

Total Sum of Interaction Cost in Tree Groups

Array Tree Depth-First Search

#214

Rank

#1271MediumFrequency: 21.5%

Web Crawler

String Depth-First Search Breadth-First Search Interactive

#215

Rank

#2126MediumFrequency: 21.5%

Count Nodes Equal to Sum of Descendants

#216

Rank

#2662MediumFrequency: 21.5%

Check Knight Tour Configuration

Array Depth-First Search Breadth-First Search Matrix Simulation

#217

Rank

#145EasyFrequency: 20.9%

Binary Tree Postorder Traversal

Stack Tree Depth-First Search Binary Tree

#218

Rank

#514HardFrequency: 20.9%

Freedom Trail

String Dynamic Programming Depth-First Search Breadth-First Search

#219

Rank

#2567MediumFrequency: 20.9%

Closest Nodes Queries in a Binary Search Tree

Array Binary Search Tree Depth-First Search Binary Search Tree Binary Tree

#220

Rank

#2641MediumFrequency: 20.9%

Disconnect Path in a Binary Matrix by at Most One Flip

Array Dynamic Programming Depth-First Search Breadth-First Search Matrix

#221

Rank

#302HardFrequency: 20.9%

Smallest Rectangle Enclosing Black Pixels

Array Binary Search Depth-First Search Breadth-First Search Matrix

#222

Rank

#2416EasyFrequency: 20.9%

Evaluate Boolean Binary Tree

#223

Rank

#685HardFrequency: 20.9%

Redundant Connection II

Depth-First Search Breadth-First Search Union-Find Graph Theory

#224

Rank

#964HardFrequency: 20.3%

Minimize Malware Spread II

Array Hash Table Depth-First Search Breadth-First Search Union-Find Graph Theory

#225

Rank

#549MediumFrequency: 20.3%

Binary Tree Longest Consecutive Sequence II

#226

Rank

#3720MediumFrequency: 20.3%

Minimize the Maximum Edge Weight of Graph

Binary Search Depth-First Search Breadth-First Search Graph Theory Shortest Path

#227

Rank

#663MediumFrequency: 20%

Equal Tree Partition

#228

Rank

#1091MediumFrequency: 20%

Maximum Average Subtree

#229

Rank

#1568MediumFrequency: 20%

Pseudo-Palindromic Paths in a Binary Tree

Bit Manipulation Tree Depth-First Search Breadth-First Search Binary Tree

#230

Rank

#1634MediumFrequency: 20%

Clone N-ary Tree

Hash Table Tree Depth-First Search Breadth-First Search

#231

Rank

#2259HardFrequency: 20%

Minimum Operations to Remove Adjacent Ones in Matrix

Array Depth-First Search Graph Theory Matrix Edmonds–Karp Algorithm MPM Algorithm Push-Relabel Algorithm Flow Network Dinic's Algorithm

#232

Rank

#799EasyFrequency: 19.5%

Minimum Distance Between BST Nodes

Tree Depth-First Search Breadth-First Search Binary Search Tree Binary Tree

#233

Rank

#770HardFrequency: 19.5%

Couples Holding Hands

Greedy Depth-First Search Breadth-First Search Union-Find Graph Theory

#234

Rank

#832MediumFrequency: 19.4%

Binary Tree Pruning

#235

Rank

#1650MediumFrequency: 18%

Find Root of N-Ary Tree

Hash Table Bit Manipulation Tree Depth-First Search

#236

Rank

#1722MediumFrequency: 18%

Throne Inheritance

Hash Table Tree Depth-First Search Design

#237

Rank

#2104MediumFrequency: 18%

Operations on Tree

Array Hash Table Tree Depth-First Search Breadth-First Search Design

#238

Rank

#669MediumFrequency: 18%

Trim a Binary Search Tree

Tree Depth-First Search Binary Search Tree Binary Tree

#239

Rank

#1747MediumFrequency: 18%

Lexicographically Smallest String After Applying Operations

String Depth-First Search Breadth-First Search Enumeration

#240

Rank

#1663MediumFrequency: 18%

Detect Cycles in 2D Grid

Array Depth-First Search Breadth-First Search Union-Find Matrix

#241

Rank

#687MediumFrequency: 16.4%

Longest Univalue Path

#242

Rank

#1248MediumFrequency: 16.4%

Binary Tree Coloring Game

#243

Rank

#1387MediumFrequency: 16.4%

Find Elements in a Contaminated Binary Tree

Hash Table Tree Depth-First Search Breadth-First Search Design Binary Tree

#244

Rank

#1655HardFrequency: 16.4%

Move Sub-Tree of N-Ary Tree

Tree Depth-First Search

#245

Rank

#1750MediumFrequency: 16.4%

Check If Two Expression Trees are Equivalent

Hash Table Tree Depth-First Search Binary Tree Counting

#246

Rank

#1796MediumFrequency: 16.4%

Correct a Binary Tree

Hash Table Tree Depth-First Search Breadth-First Search Binary Tree

#247

Rank

#1810MediumFrequency: 16.4%

Change the Root of a Binary Tree

#248

Rank

#1865HardFrequency: 16.4%

Checking Existence of Edge Length Limited Paths II

Depth-First Search Union-Find Graph Theory Design Sorting Heap (Priority Queue)Minimum Spanning Tree

#249

Rank

#1875HardFrequency: 16.4%

Tree of Coprimes

Array Math Tree Depth-First Search Number Theory

#250

Rank

#2009MediumFrequency: 16.4%

Longest Word With All Prefixes

Array String Depth-First Search Trie

#251

Rank

#2399HardFrequency: 16.4%

Minimum Flips in Binary Tree to Get Result

Dynamic Programming Tree Depth-First Search Binary Tree

#252

Rank

#2843EasyFrequency: 16.4%

Extract Kth Character From The Rope Tree

#253

Rank

#3191MediumFrequency: 16.4%

Maximum Score After Applying Operations on a Tree

Dynamic Programming Tree Depth-First Search DP on Trees

#254

Rank

#1493HardFrequency: 16.4%

Frog Position After T Seconds

Tree Depth-First Search Breadth-First Search Graph Theory

#255

Rank

#3909MediumFrequency: 16.4%

Minimum Increments to Equalize Leaf Paths

#256

Rank

#2793MediumFrequency: 16.1%

Count the Number of Complete Components

Depth-First Search Breadth-First Search Union-Find Graph Theory

#257

Rank

#1035EasyFrequency: 15.7%

Cousins in Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#258

Rank

#2582MediumFrequency: 14.6%

Minimum Score of a Path Between Two Cities

Depth-First Search Breadth-First Search Union-Find Graph Theory

#259

Rank

#904EasyFrequency: 14.4%

Leaf-Similar Trees

#260

Rank

#2438MediumFrequency: 13.2%

Find Closest Node to Given Two Nodes

Depth-First Search Graph Theory

#261

Rank

#655MediumFrequency: 12.6%

Print Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#262

Rank

#2493MediumFrequency: 12.6%

Reverse Odd Levels of Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#263

Rank

#2060HardFrequency: 12%

Merge BSTs to Create Single BST

Array Hash Table Tree Depth-First Search Binary Search Tree Binary Tree

#264

Rank

#2764MediumFrequency: 12%

Maximum Number of Fish in a Grid

Array Depth-First Search Breadth-First Search Union-Find Matrix

#265

Rank

#2409HardFrequency: 12%

Number of Increasing Paths in a Grid

Array Dynamic Programming Depth-First Search Breadth-First Search Graph Theory Topological Sort Memoization Matrix

#266

Rank

#1866MediumFrequency: 11.4%

Restore the Array From Adjacent Pairs

Array Hash Table Depth-First Search

#267

Rank

#933EasyFrequency: 10.5%

Increasing Order Search Tree

Stack Tree Depth-First Search Binary Search Tree Binary Tree

#268

Rank

#1005EasyFrequency: 10.5%

Univalued Binary Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#269

Rank

#3633MediumFrequency: 10.5%

Maximize the Number of Target Nodes After Connecting Trees I

#270

Rank

#3842HardFrequency: 10.5%

Number of Ways to Assign Edge Weights II

Array Math Dynamic Programming Bit Manipulation Tree Depth-First Search

#271

Rank

#776EasyFrequency: 10.3%

N-ary Tree Postorder Traversal

Stack Tree Depth-First Search

#272

Rank

#250MediumFrequency: 10.3%

Count Univalue Subtrees

#273

Rank

#2079HardFrequency: 8.1%

Delete Duplicate Folders in System

Array Hash Table String Depth-First Search Trie Sorting Hash Function

#274

Rank

#1309HardFrequency: 8.1%

Sort Items by Groups Respecting Dependencies

Depth-First Search Breadth-First Search Graph Theory Topological Sort Directed Acyclic Graph

#275

Rank

#3645HardFrequency: 8.1%

Maximize the Number of Target Nodes After Connecting Trees II

#276

Rank

#3900HardFrequency: 8.1%

Find Weighted Median Node in Tree

Array Binary Search Dynamic Programming Bit Manipulation Tree Depth-First Search

#277

Rank

#1484MediumFrequency: 8%

Linked List in Binary Tree

Linked List Tree Depth-First Search Binary Tree

#278

Rank

#3844MediumFrequency: 8%

Number of Ways to Assign Edge Weights I

Math Tree Depth-First Search

#279

Rank

#1474MediumFrequency: 7.3%

Longest ZigZag Path in a Binary Tree

Dynamic Programming Tree Depth-First Search Binary Tree DP on Trees

#280

Rank

#1104MediumFrequency: 7.3%

Coloring A Border

Array Depth-First Search Breadth-First Search Matrix

#281

Rank

#2439HardFrequency: 7.3%

Longest Cycle in a Graph

Depth-First Search Breadth-First Search Graph Theory Topological Sort Kosaraju's Algorithm Tarjan's SCC Algorithm

#282

Rank

#1106HardFrequency: 7.3%

Escape a Large Maze

Array Hash Table Depth-First Search Breadth-First Search Bidirectional Search

#283

Rank

#775EasyFrequency: 7.2%

N-ary Tree Preorder Traversal

Stack Tree Depth-First Search

#284

Rank

#563EasyFrequency: 7.2%

Binary Tree Tilt

#285

Rank

#774EasyFrequency: 7.2%

Maximum Depth of N-ary Tree

#286

Rank

#3561MediumFrequency: 7.2%

Remove Methods From Project

Depth-First Search Breadth-First Search Graph Theory

#287

Rank

#1969MediumFrequency: 5.5%

Maximum Number of Accepted Invitations

Array Depth-First Search Graph Theory Matrix Maximum Flow Maximum Matching Bipartite Graph Edmonds–Karp Algorithm MPM Algorithm Push-Relabel Algorithm Matching (Graph)Flow Network Dinic's Algorithm

#288

Rank

#1691HardFrequency: 5.5%

Minimum Number of Days to Disconnect Island

Array Depth-First Search Breadth-First Search Matrix Strongly Connected Component Articulation Point

#289

Rank

#3509MediumFrequency: 5.5%

K-th Largest Perfect Subtree Size in Binary Tree

Tree Depth-First Search Sorting Binary Tree

#290

Rank

#3798HardFrequency: 5.5%

Longest Special Path II

Array Hash Table Tree Depth-First Search Prefix Sum

#291

Rank

#3854HardFrequency: 5.5%

Maximum Profit from Trading Stocks with Discounts

#292

Rank

#623MediumFrequency: 5%

Add One Row to Tree

Tree Depth-First Search Breadth-First Search Binary Tree

#293

Rank

#2420HardFrequency: 5%

Closest Node to Path in Tree

Array Tree Depth-First Search Breadth-First Search

#294

Rank

#2103MediumFrequency: 5%

Find All Groups of Farmland

Array Depth-First Search Breadth-First Search Matrix

#295

Rank

#499HardFrequency: 5%

The Maze III

Array String Depth-First Search Breadth-First Search Graph Theory Heap (Priority Queue)Matrix Shortest Path Dijkstra's Algorithm Heuristic Search A* Search

#296

Rank

#3823MediumFrequency: 5%

Count Islands With Total Value Divisible by K

Array Depth-First Search Breadth-First Search Union-Find Matrix

#297

Rank

#3957HardFrequency: 5%

Sum of Perfect Square Ancestors

Array Hash Table Math Tree Depth-First Search Counting Number Theory

#298

Rank

#2445MediumFrequency: 5%

Reachable Nodes With Restrictions

Array Hash Table Tree Depth-First Search Breadth-First Search Union-Find Graph Theory

#299

Rank

#4035HardFrequency: 5%

Maximum Partition Factor

Array Binary Search Depth-First Search Breadth-First Search Union-Find Graph Theory

#300

Rank

#2201HardFrequency: 5%

Valid Arrangement of Pairs

Array Depth-First Search Graph Theory Eulerian Circuit Eulerian Path Semi-Eulerian Graph

#301

Rank

#1507MediumFrequency: 5%

Check if There is a Valid Path in a Grid

Array Depth-First Search Breadth-First Search Union-Find Matrix

#302

Rank

#3478HardFrequency: 5%

Check if the Rectangle Corner Is Reachable

Array Math Depth-First Search Breadth-First Search Union-Find Geometry

#303

Rank

#3809MediumFrequency: 5%

Properties Graph