Coding Problems

Find the maximum in each sliding window of size k

Determine if a binary tree is a valid binary search tree

Design and implement an LRU (Least Recently Used) cache

Implement a stack using two queues with push, pop, top, and empty operations

Solve the Traveling Salesman Problem using DP with bitmasking.

Count inversions in an array (how far it is from being sorted).

Count the number of 1 bits in an unsigned integer (binary representation).

Find an edge that can be removed to make a tree (detect cycle in undirected graph).

Find the smallest substring of s containing all characters of t.

Find the minimum number of jumps to reach the end of the array.

Find the length of the longest subsequence common to two strings.

Generate all possible subsets of a set (power set) using backtracking.

A peak element is greater than its neighbors. Find any peak in O(log n) time.

Sort an array of 0s, 1s, and 2s in-place using the Dutch National Flag algorithm.

Find the single number in array where others appear twice (use XOR)

Count number of islands in 2D grid using Union-Find

Find length of longest substring without repeating characters

Find minimum coins needed for amount (canonical coin system)

Maximize value in knapsack without exceeding weight capacity

Place N queens on N×N chessboard so no two queens threaten each other