Coding interview solutions

Two Sum solution

Two Sum: finding two numbers in an array that add up to a given target number

Merge Intervals solution

Given a collection of intervals, merge any overlapping intervals.

Reverse a String solution

reverse a string interview question

Longest Common Prefix solution

Find the longest common prefix string amongst an array of strings.

Palindrome String solution

Palindrome String: Free. No login required. Python technical interview question

Roman to Integer solution

Given a Roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.

Letter Combinations of a Phone Number solution

Write a function to generate all possible combinations of letters that can be formed from a given string of digits representing a phone number.

Valid Parentheses solution

valid parentheses coding question

Find the Index of the First Occurrence in a String solution

Learn how to find the index of the first occurrence of a substring in a string in this coding interview problem.

Length of Last Word solution

Find the length of the last word in a given string.

Spiral Matrix solution

given number n return matrix n by n with numbers in spiral order

FizzBuzz solution

Classic FizzBuzz: return a list from 1 to n with Fizz/Buzz substitutions.

Contains Duplicate solution

Return true if any value appears at least twice in the array.

Maximum Subarray solution

Find the contiguous subarray with the largest sum and return that sum.

Fibonacci Number solution

Return the nth Fibonacci number (0-indexed).

Factorial solution

Compute n! (the factorial of a non-negative integer n).

Move Zeroes solution

Move all zeroes to the end while keeping the order of non-zero elements.

Single Number solution

Every element appears twice except one. Find the single one.

Best Time to Buy and Sell Stock solution

Maximize profit from a single buy/sell of a stock given daily prices.

Valid Anagram solution

Determine whether one string is an anagram of another.

Binary Search solution

Return the index of target in a sorted array, or -1 if not present.

Count Vowels solution

Count the number of vowels in a string.

Climbing Stairs solution

Count distinct ways to climb n stairs taking 1 or 2 steps at a time.

Product of Array Except Self solution

Return an array where each element is the product of all others.

Trapping Rain Water solution

Given an elevation map, compute how much water it can trap after raining.

Edit Distance solution

Find the minimum number of edit operations to convert one word into another.

Median of Two Sorted Arrays solution

Find the median of two sorted arrays in logarithmic time.

Longest Valid Parentheses solution

Find the length of the longest valid well-formed parentheses substring.

Palindrome Number solution

Determine whether an integer reads the same backward as forward.

Plus One solution

Add one to a number represented as an array of digits.

Majority Element solution

Find the element that appears more than half the time in an array.

Is Subsequence solution

Check whether one string is a subsequence of another.

First Unique Character in a String solution

Find the index of the first non-repeating character in a string.

Search Insert Position solution

Return the index where a target should be inserted into a sorted array.

House Robber solution

Maximize the loot from non-adjacent houses along a street.

Jump Game solution

Decide whether you can reach the last index of an array of jump lengths.

Coin Change solution

Find the fewest coins needed to make up a given amount.

Longest Substring Without Repeating Characters solution

Find the length of the longest substring without repeating characters.

Container With Most Water solution

Find two lines that together with the x-axis hold the most water.

Number of Islands solution

Count the number of islands in a grid of land and water cells.

Word Break solution

Determine whether a string can be segmented into words from a dictionary.

Longest Increasing Subsequence solution

Find the length of the longest strictly increasing subsequence.

Largest Rectangle in Histogram solution

Find the area of the largest rectangle that fits under a histogram.

Sliding Window Maximum solution

Return the maximum of every contiguous window of size k.

Jump Game II solution

Find the minimum number of jumps needed to reach the last index.