Find the minimum number of single-character edit operations (insert, delete, or replace) required to transform one strin...
Count the number of islands in a binary matrix where 1 represents land and 0 represents water. Unlike the classic versio...
Given a list of words sorted according to an alien language, determine the order of characters in that alien alphabet. T...
Find the smallest substring that contains all unique characters present in the input string. This is a variation of the...
In a grid representing a city, 0 represents humans and 1 represents zombies. Each hour, zombies infect all adjacent huma...
Generate the nth term of the "look-and-say" sequence. The sequence starts with "1" and each subsequent term describes th...
Given an array of stock prices, find the maximum profit you can achieve by buying and selling stocks multiple times. Aft...
Given a string, determine if its characters can be rearranged to form a palindrome. A palindrome reads the same forwards...
The Missing Alphabet
MediumGiven a string containing some letters of the English alphabet, find all the missing letters from the complete alphabet...
Sort by Frequency
MediumGiven a string, sort its characters by their frequency in descending order (most frequent first). If two characters have...