DSA

Find the element that appears only once when all others appear twice using XOR

Count the number of set bits (1s) in a binary number (Hamming Weight)

Return array where ans[i] is the number of 1s in binary of i

Reverse bits of a 32-bit unsigned integer

Find the missing number in array [0, n] using XOR

Check if a number is a power of two

Add two integers without using + or - operators

Find element appearing once when others appear 3 times

Find two elements appearing once when others appear twice

Find bitwise AND of all numbers in range [left, right]

Flip all bits in binary representation

Check if a number is a power of four

Check if binary has alternating bits (101010...)

Count differing bit positions between two numbers

Find maximum XOR of any two numbers in array

Find two numbers in a sorted array that add up to target

Check if string is palindrome (ignoring non-alphanumeric)

Reverse array of characters in-place using two pointers

Remove duplicates from sorted array in-place, return new length

Move all zeroes to end while maintaining order of non-zero elements

Return squares of sorted array in sorted order (handles negatives)

Find two lines that form container holding most water

Find all unique triplets that sum to zero

Sort array of 0s, 1s, 2s in-place using three pointers

Remove all instances of value in-place, return new length

Check if s is a subsequence of t

Merge two sorted arrays into first array in-place

Partition string so each letter appears in at most one part

Calculate how much rain water can be trapped between bars

Find three integers whose sum is closest to target

Find two numbers that add up to target using hash map

Check if array contains any duplicate values using Set

Check if two strings are anagrams using character frequency

Group strings that are anagrams of each other

Find the k most frequent elements using bucket sort

Calculate product of all elements except self without division

Find length of longest consecutive sequence in O(n)

Find maximum profit from one buy and one sell

Find contiguous subarray with largest sum using Kadane algorithm

Find element appearing more than n/2 times using Boyer-Moore