Solutions Cheatsheets

Path Crossing Easy Minimum Changes To Make Alternating Binary String Easy Redistribute Characters to Make All Strings Equal Easy Longest Palindrome Easy Largest Substring Between Two Equal Characters Easy Set Mismatch Easy First Unique Character in a String Easy Intersection of Two Arrays Easy Find Common Characters Easy Number of Students Unable to Eat Lunch Easy Time Needed to Buy Tickets Easy Special Array with X Elements Greater than or Equal X Easy Count Vowel Strings in Ranges Medium Average Waiting Time Medium Sort an Array Medium Sort Colors Medium Relative Sort Array Easy Sort the People Easy Sort Array by Increasing Frequency Easy Top K Frequent Elements Medium Encode and Decode Strings Medium Range Sum Query 2D Immutable Medium Product of Array Except Self Medium Minimum Number of Operations to Move All Balls to Each Box Medium Valid Sudoku Medium Longest Consecutive Sequence Medium Encode and Decode TinyURL Medium Brick Wall Medium Best Time to Buy And Sell Stock II Medium Majority Element II Medium Minimum Index of a Valid Split Medium Subarray Sum Equals K Medium Subarray Sums Divisible by K Medium Make Sum Divisible by P Medium Unique Length 3 Palindromic Subsequences Medium Number of Sub-arrays With Odd Sum Medium Minimum Number of Swaps to Make The String Balanced Medium Number of Pairs of Interchangeable Rectangles Medium Maximum Product of The Length of Two Palindromic Subsequences Medium Grid Game Medium Find All Anagrams in a String Medium Find The Index of The First Occurrence in a String Easy Wiggle Sort Medium Largest Number Medium Continuous Subarray Sum Medium Push Dominoes Medium Repeated DNA Sequences Medium Insert Delete Get Random O(1) Medium Check if a String Contains all Binary Codes of Size K Medium Non Decreasing Array Medium Number of Ways to Split Array Medium Sign of the Product of an Array Easy Find the Difference of Two Arrays Easy Uncommon Words from Two Sentences Easy Design Parking System Easy Shifting Letters II Medium Number of Zero-Filled Subarrays Medium Word Subsets Medium Optimal Partition of String Medium Design Underground System Medium Minimum Penalty for a Shop Medium Champagne Tower Medium Sum of Absolute Differences in a Sorted Array Medium Design a Food Rating System Medium Convert an Array Into a 2D Array With Conditions Medium Minimum Number of Operations to Make Array Empty Medium Divide Array Into Arrays With Max Difference Medium Sequential Digits Medium Sort Characters By Frequency Medium Sort the Jumbled Numbers Medium Find Polygon with the Largest Perimeter Medium Minimum Remove to Make Valid Parentheses Medium Contiguous Array Medium Count Number of Bad Pairs Medium Find All Duplicates in an Array Medium Find the Length of the Longest Common Prefix Medium Count Unguarded Cells in the Grid Medium Text Justification Hard Naming a Company Hard Number of Submatrices that Sum to Target Hard First Missing Positive Hard Shortest Palindrome Hard Reverse String Easy Valid Palindrome Easy Valid Palindrome II Easy Valid Word Abbreviation Easy Merge Strings Alternately Easy Merge Sorted Array Easy Merge Two 2D Arrays by Summing Values Easy Move Zeroes Easy Remove Duplicates From Sorted Array Easy Squares of a Sorted Array Easy Assign Cookies Easy Find First Palindromic String in the Array Easy Sort Array by Parity Easy Reverse Words in a String III Easy Backspace String Compare Easy Check If Two String Arrays are Equivalent Easy Apply Operations to an Array Easy Adding Spaces to a String Medium Remove Duplicates From Sorted Array II Medium Partition Array According to Given Pivot Medium Two Sum II Input Array Is Sorted Medium 3Sum Medium 4Sum Medium Rotate Array Medium Container With Most Water Medium Number of Subsequences That Satisfy The Given Sum Condition Medium Array With Elements Not Equal to Average of Neighbors Medium Divide Players Into Teams of Equal Skill Medium Boats to Save People Medium K-th Symbol in Grammar Medium Minimum Time To Make Rope Colorful Medium Rearrange Array Elements by Sign Medium Bag of Tokens Medium Minimum Length of String after Deleting Similar Ends Medium Sentence Similarity III Medium Trapping Rain Water Hard Contains Duplicate II Easy Best Time to Buy And Sell Stock Easy Minimum Recolors to Get K Consecutive Black Blocks Easy Minimum Difference Between Highest And Lowest of K Scores Easy Number of Sub Arrays of Size K and Avg Greater than or Equal to Threshold Medium Grumpy Bookstore Owner Medium Alternating Groups II Medium Longest Substring Without Repeating Characters Medium Longest Repeating Character Replacement Medium Permutation In String Medium Frequency of The Most Frequent Element Medium Fruit into Basket Medium Maximum Number of Vowels in a Substring of Given Length Medium Minimum Number of Flips to Make The Binary String Alternating Medium Defuse the Bomb Easy Minimum Size Subarray Sum Medium Find K Closest Elements Medium Minimum Operations to Reduce X to Zero Medium Get Equal Substrings Within Budget Medium Number of Substrings Containing All Three Characters Medium Binary Subarrays with Sum Medium Count Number of Nice Subarrays Medium Subarray Product Less Than K Medium Find the Power of K-Size Subarrays I Medium Maximum Sum of Distinct Subarrays With Length K Medium Length of Longest Subarray With at Most K Frequency Medium Count Subarrays Where Max Element Appears at Least K Times Medium Maximum Beauty of an Array After Applying Operation Medium Take K of Each Character From Left and Right Medium Count of Substrings Containing Every Vowel and K Consonants II Medium Minimum Window Substring Hard Sliding Window Maximum Hard Subarrays with K Different Integers Hard Minimum Number of Operations to Make Array Continuous Hard Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit Medium Smallest Range Covering Elements from K Lists Hard Crawler Log Folder Easy Baseball Game Easy Valid Parentheses Easy Implement Stack Using Queues Easy Implement Queue using Stacks Easy Final Prices With a Special Discount in a Shop Easy Make The String Great Easy Min Stack Medium Evaluate Reverse Polish Notation Medium Removing Stars From a String Medium Validate Stack Sequences Medium Asteroid Collision Medium Daily Temperatures Medium Online Stock Span Medium Car Fleet Medium Simplify Path Medium Decode String Medium Remove K Digits Medium Remove All Adjacent Duplicates In String II Medium Reverse Substrings Between Each Pair of Parentheses Medium Minimum String Length After Removing Substrings Easy Clear Digits Easy Minimum Add to Make Parentheses Valid Medium Maximum Width Ramp Medium 132 Pattern Medium Flatten Nested List Iterator Medium Sum of Subarray Minimums Medium Maximum Frequency Stack Hard Robot Collisions Hard Largest Rectangle In Histogram Hard Shortest Subarray with Sum at Least K Hard Parsing A Boolean Expression Hard Number of Atoms Hard Binary Search Easy Search Insert Position Easy Guess Number Higher Or Lower Easy Arranging Coins Easy Valid Perfect Square Easy Sqrt(x) Easy Single Element in a Sorted Array Medium Find Peak Element Medium Successful Pairs of Spells and Potions Medium

2109. Adding Spaces to a String - Explanation

Links

Blind 75
NeetCode 150
NeetCode 250
How to use NeetCode Effectively

Socials

YouTube
LinkedIn
Twitter (X)

Contact

support@neetcode.io

Legal

Privacy Policy
Terms of Service

Copyright © 2026 neetcode.io
All rights reserved.