Combinatorics Interview Questions

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#1461HardFrequency: 53.4%

Count All Valid Pickup and Delivery Options

Asked at DoorDash

Array Math Combinatorics Fermat's Little Theorem

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#3224HardFrequency: 50.6%

Count the Number of Infection Sequences

Asked at Oracle

Rank

#3198HardFrequency: 47.5%

Number of Ways to Reach Destination in the Grid

Asked at Uber

Rank

#2324MediumFrequency: 40.8%

Find Triangular Sum of an Array

Array Math Simulation Combinatorics Number Theory

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#3604HardFrequency: 35.1%

Find the Number of Possible Ways for an Event

Rank

#956HardFrequency: 33.3%

Number of Music Playlists

Asked at Oracle

Array Math Dynamic Programming Bit Manipulation Combinatorics Bitmask

Rank

#3851HardFrequency: 31.3%

Find Sum of Array Product of Magical Sequences

Asked at Infosys

#10

Rank

#3201MediumFrequency: 30.2%

Distribute Candies Among Children II

Math Combinatorics Enumeration

#11

Rank

#1993EasyFrequency: 29.1%

Sum of All Subset XOR Totals

Array Math Backtracking Bit Manipulation Combinatorics Enumeration

#12

Rank

#3768EasyFrequency: 26.5%

Check If Digits Are Equal in String After Operations I

Math String Simulation Combinatorics Number Theory

#13

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#3414HardFrequency: 21.9%

Find Number of Ways to Reach the K-th Stair

Math Dynamic Programming Bit Manipulation Memoization Combinatorics

#14

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#1725MediumFrequency: 20%

Number of Sets of K Non-Overlapping Line Segments

Math Dynamic Programming Combinatorics Prefix Sum

#15

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#1836HardFrequency: 20%

Count Ways to Make Array With Product

Array Math Dynamic Programming Combinatorics Number Theory Prime Factorization Fermat's Little Theorem

#16

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#2738MediumFrequency: 20%

Count the Number of K-Free Subsets

Array Math Dynamic Programming Sorting Combinatorics

#17

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#3199EasyFrequency: 20%

Distribute Candies Among Children I

Math Combinatorics Enumeration

#18

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#3216HardFrequency: 20%

Distribute Candies Among Children III

Math Combinatorics

#19

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#3057HardFrequency: 19.5%

Count K-Subsequences of a String With Maximum Beauty

Hash Table Math String Greedy Sorting Combinatorics Fermat's Little Theorem

#20

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#3535HardFrequency: 19.5%

Find the Count of Monotonic Pairs I

Array Math Dynamic Programming Combinatorics Prefix Sum

#21

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#1692HardFrequency: 18%

Number of Ways to Reorder Array to Get Same BST

Array Math Divide and Conquer Dynamic Programming Tree Union-Find Binary Search Tree Memoization Combinatorics Binary Tree Fermat's Little Theorem

#22

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#1996HardFrequency: 16.4%

Number of Ways to Rearrange Sticks With K Sticks Visible

#23

Rank

#3212HardFrequency: 16.4%

Count the Number of Good Partitions

Array Hash Table Math Combinatorics

#24

Rank

#3583HardFrequency: 16.4%

Sorted GCD Pair Queries

Array Hash Table Math Binary Search Combinatorics Counting Number Theory Prefix Sum Euclidean Algorithm Greatest Common Divisor

#25

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#3637HardFrequency: 14.6%

Count Number of Balanced Permutations

Math String Dynamic Programming Combinatorics

#26

Rank

#3548HardFrequency: 14.4%

Find the Count of Good Integers

Asked at Meta

Hash Table Math Combinatorics Enumeration

#27

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#3864MediumFrequency: 10.5%

Count the Number of Computer Unlocking Permutations

Array Math Brainteaser Combinatorics

#28

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#3813HardFrequency: 10.5%

Smallest Palindromic Rearrangement II

Hash Table Math String Combinatorics Counting

#29

Rank

#4189HardFrequency: 8.1%

Find Nth Smallest Integer With K One Bits

Math Bit Manipulation Combinatorics

#30

Rank

#3682HardFrequency: 8%

Count the Number of Arrays with K Matching Adjacent Elements

Asked at Meta

Math Combinatorics Fermat's Little Theorem

#31

Rank

#2187MediumFrequency: 7.3%

Vowels of All Substrings

Asked at Microsoft

Math String Dynamic Programming Combinatorics

#32

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#1307MediumFrequency: 7.2%

Ugly Number III

Math Binary Search Combinatorics Number Theory Least Common Multiple Euclidean Algorithm Greatest Common Divisor Inclusion-Exclusion Principle

#33

Rank

#3714MediumFrequency: 7.2%

Maximum and Minimum Sums of at Most Size K Subsequences

Array Math Dynamic Programming Sorting Combinatorics

#34

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#3739HardFrequency: 5.5%

Manhattan Distances of All Arrangements of Pieces

Math Combinatorics

#35

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#2477MediumFrequency: 5.5%

Number of Ways to Reach a Position After Exactly k Steps

#36

Rank

#458HardFrequency: 5%

Poor Pigs

#37

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#3774HardFrequency: 5%

Check If Digits Are Equal in String After Operations II

Math String Combinatorics Number Theory

#38

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#1761MediumFrequency: 5%

Count Sorted Vowel Strings

#39

Rank

#489HardFrequency: 5%

Kth Smallest Instructions

Array Math Dynamic Programming Combinatorics

#40

Rank

#2605HardFrequency: 5%

Count Anagrams