Solutions

Combinations Medium Permutations Medium Subsets II Medium Permutations II Medium Generate Parentheses Medium Letter Tile Possibilities Medium Word Search Medium Palindrome Partitioning Medium Restore IP Addresses Medium Letter Combinations of a Phone Number Medium The k-th Lexicographical String of All Happy Strings of Length n Medium Matchsticks to Square Medium Splitting a String Into Descending Consecutive Values Medium Construct Smallest Number From DI String Medium Find Unique Binary String Medium Split a String Into the Max Number of Unique Substrings Medium Maximum Length of a Concatenated String With Unique Characters Medium Partition to K Equal Sum Subsets Medium The Number of Beautiful Subsets Medium Different Ways to Add Parentheses Medium Construct the Lexicographically Largest Valid Sequence Medium Count Number of Maximum Bitwise-OR Subsets Medium N Queens Hard N Queens II Hard Maximum Score Words Formed By Letters Hard Word Break II Hard

Tries

Count Prefix and Suffix Pairs I Easy Implement Trie Prefix Tree Medium Design Add And Search Words Data Structure Medium Counting Words With a Given Prefix Easy Remove Sub-Folders from the Filesystem Medium Extra Characters in a String Medium Word Search II Hard Sum of Prefix Scores of Strings Hard Count Prefix and Suffix Pairs II Hard

Graphs

Island Perimeter Easy Verifying An Alien Dictionary Easy Find the Town Judge Easy Count Servers that Communicate Medium Find Champion II Medium Number of Islands Medium Max Area of Island Medium Maximum Number of Fish in a Grid Medium Clone Graph Medium Walls And Gates Medium Rotting Oranges Medium Count Sub Islands Medium Pacific Atlantic Water Flow Medium Surrounded Regions Medium Reorder Routes to Make All Paths Lead to The City Zero Medium Snakes And Ladders Medium Open The Lock Medium Find Eventual Safe States Medium Course Schedule Medium Course Schedule II Medium Graph Valid Tree Medium Course Schedule IV Medium Check if Move Is Legal Medium Shortest Bridge Medium Shortest Path in Binary Matrix Medium Number of Connected Components In An Undirected Graph Medium Redundant Connection Medium Accounts Merge Medium Find Closest Node to Given Two Nodes Medium As Far from Land as Possible Medium Shortest Path with Alternating Colors Medium Minimum Fuel Cost to Report to the Capital Medium Minimum Score of a Path Between Two Cities Medium Number of Closed Islands Medium Number of Enclaves Medium Regions Cut By Slashes Medium Minimum Number of Vertices to Reach all Nodes Medium Is Graph Bipartite? Medium Count the Number of Complete Components Medium Evaluate Division Medium Detonate the Maximum Bombs Medium Find All Possible Recipes from Given Supplies Medium Shortest Distance After Road Addition Queries I Medium Minimum Height Trees Medium Path with Maximum Gold Medium Most Profitable Path in a Tree Medium Maximum Number of Points From Grid Queries Hard Maximum Number of K-Divisible Components Hard Sliding Puzzle Hard Largest Color Value in a Directed Graph Hard Minimum Number of Days to Eat N Oranges Hard Find All People With Secret Hard Word Ladder Hard Parallel Courses III Hard

Advanced Graphs

Path with Minimum Effort Medium Network Delay Time Medium Reconstruct Itinerary Hard Min Cost to Connect All Points Medium Path with Maximum Probability Medium Find the Safest Path in a Grid Medium Swim In Rising Water Hard Alien Dictionary Hard Trapping Rain Water II Hard Minimum Obstacle Removal to Reach Corner Hard Minimum Cost to Make at Least One Valid Path in a Grid Hard Minimum Time to Visit a Cell In a Grid Hard Cheapest Flights Within K Stops Medium Find the City With the Smallest Number of Neighbors at a Threshold Distance Medium Minimum Cost to Convert String I Medium Number of Ways to Arrive at Destination Medium Making A Large Island Hard Minimum Cost Walk in Weighted Graph Hard Number of Good Paths Hard Maximum Employees to Be Invited to a Meeting Hard Remove Max Number of Edges to Keep Graph Fully Traversable Hard Minimum Number of Days to Disconnect Island Hard Second Minimum Time to Reach Destination Hard Find Minimum Diameter After Merging Two Trees Hard Find Critical and Pseudo Critical Edges in Minimum Spanning Tree Hard Build a Matrix With Conditions Hard Greatest Common Divisor Traversal Hard Divide Nodes Into the Maximum Number of Groups Hard

1-D Dynamic Programming

Climbing Stairs Easy Min Cost Climbing Stairs Easy N-th Tribonacci Number Easy House Robber Medium House Robber II Medium Longest Palindromic Substring Medium Palindromic Substrings Medium Decode Ways Medium Coin Change Medium Maximum Product Subarray Medium Word Break Medium Longest Increasing Subsequence Medium Partition Equal Subset Sum Medium Triangle Medium Delete And Earn Medium Paint House Medium Filling Bookcase Shelves Medium Combination Sum IV Medium Perfect Squares Medium Check if There is a Valid Partition For The Array Medium Maximum Subarray Min Product Medium Minimum Cost For Tickets Medium Integer Break Medium Number of Longest Increasing Subsequence Medium Stickers to Spell Word Hard Uncrossed Lines Medium Solving Questions With Brainpower Medium Count Ways to Build Good Strings Medium Ugly Number II Medium New 21 Game Medium Best Team with no Conflicts Medium Longest String Chain Medium Knight Dialer Medium Partition Array for Maximum Sum Medium Largest Divisible Subset Medium Stone Game III Hard Concatenated Words Hard Maximize Score after N Operations Hard Find the Longest Valid Obstacle Course at Each Position Hard Minimum Number of Removals to Make Mountain Array Hard Count all Valid Pickup and Delivery Options Hard Number of Ways to Divide a Long Corridor Hard Maximum Sum of 3 Non-Overlapping Subarrays Hard Maximum Profit in Job Scheduling Hard Student Attendance Record II Hard

2-D Dynamic Programming

Unique Paths Medium Unique Paths II Medium Minimum Path Sum Medium Maximum Number of Points with Cost Medium Longest Common Subsequence Medium Longest Palindromic Subsequence Medium Length of Longest Fibonacci Subsequence Medium Last Stone Weight II Medium Best Time to Buy And Sell Stock With Cooldown Medium Coin Change II Medium Target Sum Medium Interleaving String Medium Stone Game Medium Stone Game II Medium Longest Increasing Path In a Matrix Hard Maximal Square Medium Count Square Submatrices with All Ones Medium Ones and Zeroes Medium 2 Keys Keyboard Medium Maximum Alternating Subsequence Sum Medium Distinct Subsequences Hard Edit Distance Medium Number of Dice Rolls with Target Sum Medium Minimum Falling Path Sum Medium Out of Boundary Paths Medium Longest Ideal Subsequence Medium Count Number of Teams Medium Shortest Common Supersequence Hard Count Vowels Permutation Hard Burst Balloons Hard Number of Ways to Rearrange Sticks With K Sticks Visible Hard Regular Expression Matching Hard Flip String to Monotone Increasing Medium

407. Trapping Rain Water II - Explanation

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