Coders Crushby Napplied AI

Data Structures & Algorithms

100+ curated problems from top tech interviews

AllArrays & HashingTwo PointersSliding WindowStack & QueueBinary SearchLinked ListsTreesTriesHeap / Priority QueueGraphsDynamic ProgrammingBacktrackingGreedyIntervalsMath & GeometryBit Manipulation

11 problems found

3Sum

MediumTwo Pointers

Find all unique triplets summing to 0...

O(n²) / O(1)
Google, Facebook

Remove Nth Node From End of List

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MediumTwo Pointers

Remove nth node from linked list...

O(n) / O(1)
Google, Apple

4Sum

MediumTwo Pointers

Find all unique quadruplets...

O(n³) / O(1)
Google, Facebook

Is Palindrome II

EasyTwo Pointers

Check palindrome with alphanumeric only...

O(n) / O(1)
Facebook, Apple

Reverse String

EasyTwo Pointers

Reverse character array in-place...

O(n) / O(1)
Google, Amazon

Two Sum II Input Array Sorted

EasyTwo Pointers

Find two numbers in sorted array...

O(n log n) / O(n)
Amazon, Google

Merge Sorted Array

EasyTwo Pointers

Merge two sorted arrays in-place...

O(n log n) / O(n)
Google, Microsoft

Container With Most Water

#11
MediumTwo Pointers

You are given an integer array height of length n. There are n vertical lines drawn such that the two endpoints of the ith line are (i, 0) and (i, hei...

O(n) / O(1)
Google, Amazon

Valid Palindrome

#125
EasyTwo Pointers

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the ...

O(n) / O(1)
Google, Amazon

3Sum

#15
MediumTwo Pointers

Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k]...

O(n²) / O(1)
Google, Amazon

Trapping Rain Water

#42
HardTwo Pointers

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining....

O(n) / O(1)
Google, Amazon