LeetCode 1096: Brace Expansion II
A clear explanation of generating all strings from a brace expansion expression using recursive parsing and set union/concatenation.
Tag
Backtracking
57 notes
LeetCode 1088: Confusing Number II
A clear explanation of counting confusing numbers up to n using digit backtracking with rotation validation.
LeetCode 1087: Brace Expansion
A clear explanation of generating all strings from a brace expansion pattern in lexicographic order using backtracking.
LeetCode 1079: Letter Tile Possibilities
A clear explanation of counting all distinct non-empty sequences from a set of letter tiles using backtracking with frequency counting.
LeetCode 282: Expression Add Operators
A backtracking solution for inserting operators into a numeric string so the expression evaluates to a target value.
LeetCode 113: Path Sum II
A clear explanation of finding all root-to-leaf paths whose values add up to a target sum using depth-first search and backtracking.
LeetCode 967: Numbers With Same Consecutive Differences
A clear explanation of generating all n-digit numbers whose adjacent digits differ by k.
LeetCode 842: Split Array into Fibonacci Sequence
A clear explanation of the Split Array into Fibonacci Sequence problem using backtracking, leading-zero checks, and 32-bit integer limits.
LeetCode 996: Number of Squareful Arrays
A clear explanation of counting unique permutations where every adjacent pair sums to a perfect square using backtracking.
LeetCode 980: Unique Paths III
A clear explanation of counting all paths from start to end that visit every non-obstacle square exactly once using backtracking.
LeetCode 816: Ambiguous Coordinates
An enumeration solution for reconstructing all valid coordinate pairs after commas, spaces, and decimal points were removed.
LeetCode 797: All Paths From Source to Target
A clear explanation of finding every path from node 0 to node n - 1 in a directed acyclic graph using DFS and backtracking.
LeetCode 784: Letter Case Permutation
A clear explanation of generating all strings formed by independently changing each letter to lowercase or uppercase.
LeetCode 756: Pyramid Transition Matrix
A clear explanation of solving Pyramid Transition Matrix using backtracking and memoization over pyramid rows.
LeetCode 698: Partition to K Equal Sum Subsets
Decide whether an array can be divided into k non-empty subsets with equal sums using backtracking and pruning.
LeetCode 679: 24 Game
Determine whether four numbers can be combined with arithmetic operations and parentheses to produce 24.
LeetCode 638: Shopping Offers
A DFS and memoization solution for finding the minimum cost to satisfy item needs using individual prices and reusable special offers.
LeetCode 47: Permutations II
A clear explanation of Permutations II using sorting, depth-first search, and duplicate-skipping backtracking.
LeetCode 46: Permutations
A clear explanation of Permutations using depth-first search and backtracking.
LeetCode 526: Beautiful Arrangement
A clear explanation of counting beautiful arrangements using backtracking and divisibility pruning.
LeetCode 494: Target Sum
A clear explanation of counting sign assignments that reach a target using recursion first, then subset-sum dynamic programming.
LeetCode 491: Non-decreasing Subsequences
A clear explanation of generating all distinct non-decreasing subsequences using DFS, backtracking, and per-level duplicate control.
LeetCode 489: Robot Room Cleaner
A clear explanation of cleaning an unknown grid using DFS, relative coordinates, and physical backtracking.
LeetCode 488: Zuma Game
A clear explanation of solving Zuma Game with DFS, memoization, and chain-removal simulation.
LeetCode 473: Matchsticks to Square
A clear explanation of deciding whether matchsticks can form a square using backtracking, sorting, and pruning.
LeetCode 465: Optimal Account Balancing
A clear explanation of minimizing debt-settlement transactions using net balances, backtracking, and memoization-style pruning.
LeetCode 425: Word Squares
A clear explanation of building all word squares using backtracking with prefix pruning.
LeetCode 411: Minimum Unique Word Abbreviation
A clear explanation of finding the shortest abbreviation that does not conflict with any dictionary word using bit masks.
LeetCode 351: Android Unlock Patterns
A clear explanation of Android Unlock Patterns using backtracking, a jump table, and symmetry optimization.
LeetCode 320: Generalized Abbreviation
A clear explanation of Generalized Abbreviation using backtracking to choose whether each character is kept or abbreviated.
LeetCode 306: Additive Number
A clear explanation of Additive Number using split enumeration and deterministic checking.
LeetCode 301: Remove Invalid Parentheses
A clear explanation of Remove Invalid Parentheses using BFS to guarantee the minimum number of removals.
LeetCode 294: Flip Game II
A recursive game theory solution with memoization for deciding whether the starting player can force a win.
LeetCode 291: Word Pattern II
A backtracking solution for matching a pattern string to a target string using a bijective character-to-substring mapping.
LeetCode 267: Palindrome Permutation II
A clear explanation of the Palindrome Permutation II problem using character counts and backtracking over half of the palindrome.
LeetCode 257: Binary Tree Paths
A clear explanation of the Binary Tree Paths problem using DFS backtracking to collect every root-to-leaf path.
LeetCode 254: Factor Combinations
A clear explanation of the Factor Combinations problem using DFS backtracking with non-decreasing factors.
LeetCode 216: Combination Sum III
A clear explanation of finding k distinct numbers from 1 to 9 that sum to n using backtracking.
LeetCode 212: Word Search II
A clear explanation of finding multiple words in a character board using a Trie and DFS backtracking.
LeetCode 211: Design Add and Search Words Data Structure
A clear explanation of designing a word dictionary with addWord and wildcard search using a Trie and DFS.
LeetCode 95: Unique Binary Search Trees II
A detailed guide to solving Unique Binary Search Trees II with recursive tree generation over value ranges.
LeetCode 93: Restore IP Addresses
A detailed guide to solving Restore IP Addresses with backtracking over four valid IP segments.
LeetCode 90: Subsets II
A detailed guide to solving Subsets II with sorting, backtracking, and duplicate skipping.
LeetCode 89: Gray Code
A detailed guide to solving Gray Code using the binary-to-Gray-code formula.
LeetCode 79: Word Search
A detailed guide to solving Word Search with depth-first search and backtracking on a grid.
LeetCode 78: Subsets
A detailed guide to solving Subsets with backtracking and the include-or-skip recursion idea.
LeetCode 77: Combinations
A detailed guide to solving Combinations with backtracking and pruning.
LeetCode 140: Word Break II
Return all valid sentences formed by inserting spaces into a string so every word belongs to the dictionary, using DFS with memoization.
LeetCode 131: Palindrome Partitioning
Generate all ways to split a string so that every piece is a palindrome, using backtracking with palindrome precomputation.
LeetCode 126: Word Ladder II
Find all shortest word transformation sequences using BFS to build shortest-path parents, then backtracking to reconstruct every answer.
LeetCode 52: N-Queens II
A clear guide to solving N-Queens II by counting valid queen placements with backtracking.
LeetCode 51: N-Queens
A clear guide to solving N-Queens with backtracking, row-by-row placement, and constant-time conflict checks.
LeetCode 40: Combination Sum II
A clear explanation of finding unique combinations that sum to a target when each array element may be used at most once.
LeetCode 39: Combination Sum
A clear explanation of finding all unique combinations that sum to a target using backtracking.
LeetCode 37: Sudoku Solver
A clear explanation of solving a Sudoku board using backtracking and constraint checking.
LeetCode 22: Generate Parentheses
A detailed explanation of generating all well-formed parentheses strings using backtracking.
LeetCode 17: Letter Combinations of a Phone Number
A detailed explanation of generating all possible phone keypad letter combinations using backtracking.