The “String Compression” problem requires reducing the size of a character array by compressing consecutive repeating characters into a single character followed by their count. For example, the [“a”, “a”, “b”, “b”, “b”, “c”] should be compressed to [“a”, “2”, “b”, “3”, “c”]. The challenge is to perform this compression…
Reverse Integer – 7. LeetCode
The Reverse Integer problem asks us to take an integer as input and return its digits reversed. For example, if the input is 123, the output should be 321. If the input is negative, like -123, the output should be -321. There is a constraint: if reversing the integer causes…
Summary Ranges – 228. LeetCode
The Summary Ranges problem asks us to take a sorted list of integers and group consecutive numbers into ranges. For example, given the input [0, 1, 2, 4, 5, 7], the output would be [“0->2”, “4->5”, “7”]. The goal is to find and summarize sequences of consecutive numbers in a…
Insert Interval – 56. LeetCode
The Insert Interval problem involves inserting a new interval into a sorted list of non-overlapping intervals and merging any overlapping intervals. Think of it like scheduling a new meeting in a calendar: you add the meeting and merge it with existing ones if they overlap, ensuring the schedule remains clean…
N-Queens – 51. LeetCode
The N-Queens problems asks us to place N queens on an N * N chessboard such that no two queens threaten each other. The means no two queens can be in the the same row, column, or diagonal. The challenge is to find all possible configurations of the board that…
Time Based Key-Value Store – 981. LeetCode
The “Time Based Key-Value Store” problem requires creating a data structure where you can store multiple values for the same key but with different timestamps. Later, you can retrieve the value of a key at a specific timestamp, either exactly or the closest one before it. Think of it as…
Longest Repeating Character Replacement – 424. LeetCode
The Longest Repeating Character Replacement problem asks us to find the length of the longest substring in a string s that can be transformed into a substring with all identical characters by replacing at most k characters. For example, in the string “AABABBA” with k = 1, the longest substring…
Valid Anagram – 242. Leetcode
An anagram is a word or phrase formed by rearranging the letters of another word or phrase. For example, “listen” and “silent” are anagrams. This problem asks you to determine if two given strings are anagrams of each other, but it should also work with Unicode characters like emojis or…
First Unique Character In A String – 387. LeetCode
The “First Unique Character in a String” problem asks you to find the index of the first character in a string that appears only one. If no such character exists, return -1. This problem is about efficiently identifying a character that is unique while processing all the characters in the…
Search In Rotated Sorted Array – 33. LeetCode
The “Search in Rotated Sorted Array” problem involves finding a target value in a sorted array that’s been rotated at some unknown pivot. For instance, an array like [4,5,6,7,0,1,2] is a rotation of [0,1,2,4,5,6,7]. You’re given this rotated array and a target value; your goal is to determine the target’s…
