Coding Interview Questions

Determine if an array of integers contains any duplicate values.

Check if two strings are anagrams of each other.

Find indices of two numbers in an array that add up to a specific target.

Group an array of strings by their anagrams.

Find the k most frequent elements in an array.

Design an algorithm to encode a list of strings to a single string and decode it back.

Compute an array where each element is the product of all other elements.

Find the length of the longest sequence of consecutive elements in an unsorted array.

Check if a string is a palindrome, ignoring case and non-alphanumeric characters.

Find all unique triplets in the array which give the sum of zero.

Find two lines that together with the x-axis form a container, such that the container contains the most water.

Find the maximum profit that can be achieved by buying and selling a stock once.

Find the length of the longest substring without repeating characters.

Find the longest substring with the same letter after at most k replacements.

Find the smallest substring that contains all characters of another string.

Determine if a string of parentheses, brackets, and braces is valid.

Find the minimum element in a sorted array that has been rotated.

Search for a target value in a sorted array that has been rotated.

Reverse a singly linked list.

Merge two sorted linked lists into one sorted list.

Determine if a linked list has a cycle in it.

Reorder a linked list to be L0→Ln→L1→Ln-1→L2→Ln-2→…

Remove the nth node from the end of a linked list.

Merge k sorted linked lists into one sorted linked list.

Invert a binary tree by swapping its left and right children.

Find the maximum depth or height of a binary tree.

Check if two binary trees are structurally identical and have the same node values.

Check if a binary tree has another tree as its subtree.

Find the lowest common ancestor (LCA) of two given nodes in a Binary Search Tree.

Traverse a binary tree level by level.

Determine if a binary tree is a valid binary search tree (BST).

Find the kth smallest element in a Binary Search Tree.

Reconstruct a binary tree from its preorder and inorder traversal sequences.

Find the maximum path sum in a binary tree. The path may start and end at any node.

Design an algorithm to serialize a binary tree to a string and deserialize it back.

Design a data structure that supports adding numbers and finding the median efficiently.

Find all unique combinations in a set of candidates that sum up to a target.

Find if a word exists in a grid of characters.

Implement a trie data structure with insert, search, and startsWith methods.

Design a data structure that supports adding words and searching with wildcards.

Find all words from a dictionary that exist in a grid of characters.

Count the number of islands in a 2D grid.

Make a deep copy of an undirected graph.

Find all cells in a grid from which water can flow to both oceans.

Determine if you can finish all courses given a set of prerequisites.