LeetCode 971: Flip Binary Tree To Match Preorder Traversal
A clear explanation of matching a binary tree preorder traversal by greedily flipping nodes.
Tag
Depth-First-Search
51 notes
LeetCode 968: Binary Tree Cameras
A clear explanation of placing the minimum number of cameras in a binary tree using postorder DFS.
LeetCode 967: Numbers With Same Consecutive Differences
A clear explanation of generating all n-digit numbers whose adjacent digits differ by k.
LeetCode 965: Univalued Binary Tree
A clear explanation of checking whether every node in a binary tree has the same value.
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 841: Keys and Rooms
A clear explanation of the Keys and Rooms problem using graph traversal from room 0.
LeetCode 839: Similar String Groups
A clear explanation of the Similar String Groups problem using graph connectivity and union-find.
LeetCode 834: Sum of Distances in Tree
A clear explanation of the Sum of Distances in Tree problem using tree DP, subtree sizes, and rerooting.
LeetCode 827: Making A Large Island
A clear explanation of the Making A Large Island problem using connected component labeling and island size lookup.
LeetCode 924: Minimize Malware Spread
A clear explanation of minimizing malware spread by analyzing connected components with Union Find.
LeetCode 993: Cousins in Binary Tree
A clear explanation of checking whether two binary tree nodes are cousins using BFS with parent tracking.
LeetCode 988: Smallest String Starting From Leaf
A clear explanation of finding the lexicographically smallest leaf-to-root string in a binary tree using DFS.
LeetCode 987: Vertical Order Traversal of a Binary Tree
A clear explanation of vertical tree traversal using coordinates, DFS, sorting, and column grouping.
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 979: Distribute Coins in Binary Tree
A clear explanation of balancing coins in a binary tree using postorder DFS and subtree coin balance.
LeetCode 947: Most Stones Removed with Same Row or Column
A clear explanation of solving Most Stones Removed with Same Row or Column using connected components and union-find.
LeetCode 938: Range Sum of BST
A clear explanation of solving Range Sum of BST using DFS with binary search tree pruning.
LeetCode 934: Shortest Bridge
A clear explanation of solving Shortest Bridge using DFS to mark one island and BFS to expand toward the other island.
LeetCode 928: Minimize Malware Spread II
A clear explanation of solving Minimize Malware Spread II by removing each infected node and simulating the final malware spread.
LeetCode 749: Contain Virus
Simulate virus containment by repeatedly quarantining the most dangerous infected region and spreading the remaining regions.
LeetCode 742: Closest Leaf in a Binary Tree
Find the nearest leaf to a target node by converting the tree into an undirected graph and running breadth-first search.
LeetCode 733: Flood Fill
Recolor the connected component containing the starting pixel using depth-first search.
LeetCode 671: Second Minimum Node In a Binary Tree
A clear explanation of finding the second minimum value in a special binary tree using DFS.
LeetCode 669: Trim a Binary Search Tree
A clear explanation of trimming a BST so that all remaining node values lie inside a given inclusive range.
LeetCode 666: Path Sum IV
A clear explanation of computing all root-to-leaf path sums from a compact three-digit binary tree encoding.
LeetCode 663: Equal Tree Partition
A clear explanation of checking whether a binary tree can be split into two equal-sum trees by removing one edge.
LeetCode 655: Print Binary Tree
A clear explanation of formatting a binary tree into a 2D string matrix using tree height and recursive placement.
LeetCode 653: Two Sum IV - Input is a BST
A clear explanation of finding whether two different nodes in a binary search tree sum to a target value.
LeetCode 652: Find Duplicate Subtrees
A clear explanation of finding duplicate binary tree subtrees using postorder traversal, serialization, and a hash map.
LeetCode 572: Subtree of Another Tree
A clear explanation of Subtree of Another Tree using recursive tree matching and DFS.
LeetCode 565: Array Nesting
A clear explanation of Array Nesting using cycle detection over a permutation.
LeetCode 563: Binary Tree Tilt
A clear explanation of Binary Tree Tilt using postorder DFS to compute subtree sums and accumulate tilt.
LeetCode 559: Maximum Depth of N-ary Tree
A clear explanation of Maximum Depth of N-ary Tree using recursive depth-first search.
LeetCode 549: Binary Tree Longest Consecutive Sequence II
A clear explanation of finding the longest increasing or decreasing consecutive path in a binary tree using DFS.
LeetCode 547: Number of Provinces
A clear explanation of counting connected components in an undirected graph represented by an adjacency matrix.
LeetCode 545: Boundary of Binary Tree
A clear explanation of collecting the boundary of a binary tree using separate left boundary, leaves, and right boundary traversals.
LeetCode 543: Diameter of Binary Tree
A clear explanation of finding the longest path between any two nodes in a binary tree using DFS height computation.
LeetCode 538: Convert BST to Greater Tree
A clear explanation of converting a BST into a greater tree using reverse inorder traversal and a running sum.
LeetCode 530: Minimum Absolute Difference in BST
A clear explanation of finding the minimum difference between two BST node values using inorder traversal.
LeetCode 529: Minesweeper
A clear explanation of updating a Minesweeper board using DFS flood fill and adjacent mine counting.
LeetCode 386: Lexicographical Numbers
A clear explanation of generating numbers from 1 to n in lexicographical order using an iterative DFS-style traversal.
LeetCode 339: Nested List Weight Sum
A clear explanation of Nested List Weight Sum using depth-first search over a nested structure.
LeetCode 100: Same Tree
A detailed guide to solving Same Tree with recursive DFS and structural comparison.
LeetCode 99: Recover Binary Search Tree
A detailed guide to solving Recover Binary Search Tree with inorder traversal and two misplaced nodes.
LeetCode 98: Validate Binary Search Tree
A detailed guide to solving Validate Binary Search Tree with recursive lower and upper bounds.
LeetCode 94: Binary Tree Inorder Traversal
A detailed guide to solving Binary Tree Inorder Traversal with recursion and an iterative stack.
LeetCode 79: Word Search
A detailed guide to solving Word Search with depth-first search and backtracking on a grid.
LeetCode 200: Number of Islands
A clear explanation of counting connected groups of land cells in a grid using DFS or BFS.
LeetCode 199: Binary Tree Right Side View
A clear explanation of returning the visible nodes from the right side of a binary tree using level-order traversal.
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.