LeetCode 971: Flip Binary Tree To Match Preorder Traversal
A clear explanation of matching a binary tree preorder traversal by greedily flipping nodes.
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Tree
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LeetCode 968: Binary Tree Cameras
A clear explanation of placing the minimum number of cameras in a binary tree using postorder DFS.
LeetCode 965: Univalued Binary Tree
A clear explanation of checking whether every node in a binary tree has the same value.
LeetCode 958: Check Completeness of a Binary Tree
A clear explanation of checking whether a binary tree is complete using level-order traversal.
LeetCode 951: Flip Equivalent Binary Trees
A clear explanation of checking whether two binary trees are equivalent after swapping left and right children at any number of nodes.
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 919: Complete Binary Tree Inserter
A clear explanation of maintaining a complete binary tree inserter using level-order indexing.
LeetCode 897: Increasing Order Search Tree
A clear explanation of rearranging a binary search tree into an increasing right-only tree using inorder traversal.
LeetCode 894: All Possible Full Binary Trees
A clear explanation of generating all full binary trees with n nodes using recursion and memoization.
LeetCode 889: Construct Binary Tree from Preorder and Postorder Traversal
A clear explanation of reconstructing a binary tree from preorder and postorder traversals using recursion and index ranges.
LeetCode 623: Add One Row to Tree
A clear explanation of Add One Row to Tree using tree traversal and careful subtree reconnection.
LeetCode 998: Maximum Binary Tree II
A clear explanation of inserting a value into a maximum binary tree by following the right spine.
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 979: Distribute Coins in Binary Tree
A clear explanation of balancing coins in a binary tree using postorder DFS and subtree coin balance.
LeetCode 872: Leaf-Similar Trees
A clear explanation of comparing two binary trees by collecting their leaf value sequences with DFS.
LeetCode 865: Smallest Subtree with all the Deepest Nodes
A clear explanation of finding the smallest subtree that contains all deepest nodes using bottom-up DFS.
LeetCode 938: Range Sum of BST
A clear explanation of solving Range Sum of BST using DFS with binary search tree pruning.
LeetCode 783: Minimum Distance Between BST Nodes
A clear explanation of finding the minimum difference between any two nodes in a BST using inorder traversal.
LeetCode 776: Split BST
A clear explanation of splitting a binary search tree into two BSTs using recursion and pointer rewiring.
LeetCode 701: Insert into a Binary Search Tree
A clear explanation of inserting a value into a binary search tree using recursive and iterative traversal.
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 690: Employee Importance
Compute the total importance of an employee and all direct and indirect subordinates using a hash map and 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 662: Maximum Width of Binary Tree
A clear explanation of computing the maximum width of a binary tree using level-order traversal and complete-tree indices.
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 654: Maximum Binary Tree
A clear explanation of constructing a maximum binary tree recursively using divide and conquer.
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 637: Average of Levels in Binary Tree
A breadth-first search solution for computing the average value of nodes at each level of a binary tree.
LeetCode 617: Merge Two Binary Trees
A recursive tree traversal guide for merging two binary trees node by node.
LeetCode 606: Construct String from Binary Tree
A recursive guide for converting a binary tree into a preorder parenthesized string while preserving the one-to-one mapping between the tree and the string.
LeetCode 236: Lowest Common Ancestor of a Binary Tree
A clear explanation of finding the lowest common ancestor in a normal binary tree using recursive depth-first search.
LeetCode 235: Lowest Common Ancestor of a Binary Search Tree
A clear explanation of finding the lowest common ancestor in a binary search tree using BST ordering properties.
LeetCode 230: Kth Smallest Element in a BST
A clear explanation of finding the kth smallest value in a binary search tree using inorder traversal.
LeetCode 700: Search in a Binary Search Tree
Search for a target value in a binary search tree and return the subtree rooted at the matching node.
LeetCode 687: Longest Univalue Path
Find the longest path in a binary tree where every node on the path has the same value using depth-first search.
LeetCode 590: N-ary Tree Postorder Traversal
A clear DFS solution for returning the postorder traversal of an N-ary tree.
LeetCode 589: N-ary Tree Preorder Traversal
A clear DFS solution for returning the preorder traversal of an N-ary tree.
LeetCode 582: Kill Process
A clear graph traversal solution for finding all processes terminated when killing a target process.
LeetCode 572: Subtree of Another Tree
A clear explanation of Subtree of Another Tree using recursive tree matching and DFS.
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 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 536: Construct Binary Tree from String
A clear explanation of parsing a parenthesized string recursively to construct a binary tree.
LeetCode 530: Minimum Absolute Difference in BST
A clear explanation of finding the minimum difference between two BST node values using inorder traversal.
LeetCode 515: Find Largest Value in Each Tree Row
A clear explanation of finding the maximum value at every depth of a binary tree using level-order traversal.
LeetCode 513: Find Bottom Left Tree Value
A clear explanation of finding the leftmost value in the deepest row of a binary tree using level-order traversal.
LeetCode 510: Inorder Successor in BST II
A clear explanation of finding the inorder successor in a binary search tree when nodes contain parent pointers.
LeetCode 508: Most Frequent Subtree Sum
A clear explanation of finding the most frequent subtree sum in a binary tree using postorder DFS and a frequency map.
LeetCode 558: Logical OR of Two Binary Grids Represented as Quad-Trees
A clear explanation of merging two quad-trees using recursive logical OR operations.
LeetCode 450: Delete Node in a BST
Delete a node from a binary search tree while preserving the BST property using recursive search and inorder successor replacement.
LeetCode 449: Serialize and Deserialize BST
Serialize a binary search tree compactly with preorder traversal and rebuild it using BST value bounds.
LeetCode 437: Path Sum III
Count downward paths in a binary tree whose values sum to targetSum using DFS and prefix sums.
LeetCode 431: Encode N-ary Tree to Binary Tree
Convert an N-ary tree into a binary tree and reconstruct it using the left-child right-sibling representation.
LeetCode 429: N-ary Tree Level Order Traversal
Traverse an N-ary tree level by level using breadth-first search.
LeetCode 428: Serialize and Deserialize N-ary Tree
Serialize an N-ary tree into a string and reconstruct the same tree using preorder traversal with child counts.
LeetCode 427: Construct Quad Tree
Build a quad tree from a binary square grid using recursive divide and conquer.
LeetCode 426: Convert Binary Search Tree to Sorted Doubly Linked List
Convert a BST into a sorted circular doubly linked list in-place using inorder traversal.
LeetCode 404: Sum of Left Leaves
A clear explanation of the Sum of Left Leaves problem using depth-first traversal of a binary tree.
LeetCode 366: Find Leaves of Binary Tree
A clear explanation of grouping binary tree nodes by the round in which they become leaves using postorder DFS.
LeetCode 364: Nested List Weight Sum II
A clear explanation of computing inverse depth weighted sum using level-order traversal.
LeetCode 337: House Robber III
A clear explanation of House Robber III using tree dynamic programming with rob and skip states.
LeetCode 333: Largest BST Subtree
A clear explanation of Largest BST Subtree using postorder traversal and subtree state propagation.
LeetCode 331: Verify Preorder Serialization of a Binary Tree
A clear explanation of verifying preorder serialization using slot counting without reconstructing the tree.
LeetCode 314: Binary Tree Vertical Order Traversal
A clear explanation of Binary Tree Vertical Order Traversal using BFS with column indices.
LeetCode 310: Minimum Height Trees
A clear explanation of Minimum Height Trees using leaf trimming to find the center of a tree.
LeetCode 298: Binary Tree Longest Consecutive Sequence
A DFS solution for finding the longest parent-to-child path where each node value increases by exactly one.
LeetCode 297: Serialize and Deserialize Binary Tree
A preorder DFS codec for converting a binary tree to a string and reconstructing the same tree from that string.
LeetCode 285: Inorder Successor in BST
A binary-search-style solution for finding the smallest node greater than p in a binary search tree.
LeetCode 272: Closest Binary Search Tree Value II
A clear explanation of the Closest Binary Search Tree Value II problem using inorder traversal and a fixed-size sliding window.
LeetCode 270: Closest Binary Search Tree Value
A clear explanation of the Closest Binary Search Tree Value problem using the BST property to walk toward the target.
LeetCode 261: Graph Valid Tree
A clear explanation of the Graph Valid Tree problem using Union Find to detect cycles and verify connectivity.
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 255: Verify Preorder Sequence in Binary Search Tree
A clear explanation of the Verify Preorder Sequence in Binary Search Tree problem using a monotonic stack and lower bound tracking.
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 96: Unique Binary Search Trees
A detailed guide to solving Unique Binary Search Trees with dynamic programming and the Catalan recurrence.
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 173: Binary Search Tree Iterator
A clear explanation of designing an iterator over a BST using controlled inorder traversal with a stack.
LeetCode 145: Binary Tree Postorder Traversal
Return the postorder traversal of a binary tree using recursion or an iterative stack-based approach.
LeetCode 144: Binary Tree Preorder Traversal
Return the preorder traversal of a binary tree using recursion or an explicit stack.
LeetCode 129: Sum Root to Leaf Numbers
Compute the sum of all numbers formed by root-to-leaf paths using depth-first search and decimal accumulation.
LeetCode 124: Binary Tree Maximum Path Sum
A clear explanation of finding the maximum path sum in a binary tree using bottom-up depth-first search.
LeetCode 117: Populating Next Right Pointers in Each Node II
A clear explanation of connecting next pointers in any binary tree using constant extra space.
LeetCode 116: Populating Next Right Pointers in Each Node
A clear explanation of connecting next pointers in a perfect binary tree using constant extra space.
LeetCode 114: Flatten Binary Tree to Linked List
A clear explanation of flattening a binary tree into a linked list in preorder traversal order using recursive depth-first search.
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 112: Path Sum
A clear explanation of checking whether a binary tree has a root-to-leaf path whose values add up to a target sum.
LeetCode 111: Minimum Depth of Binary Tree
A clear explanation of finding the minimum depth of a binary tree using breadth-first search.
LeetCode 110: Balanced Binary Tree
A clear explanation of checking whether a binary tree is height-balanced using bottom-up depth-first search.
LeetCode 109: Convert Sorted List to Binary Search Tree
A clear explanation of converting a sorted linked list into a height-balanced binary search tree using slow and fast pointers.
LeetCode 108: Convert Sorted Array to Binary Search Tree
A clear explanation of building a height-balanced binary search tree from a sorted array using divide and conquer.
LeetCode 107: Binary Tree Level Order Traversal II
A clear explanation of returning binary tree levels from bottom to top using breadth-first search.
LeetCode 106: Construct Binary Tree from Inorder and Postorder Traversal
A clear explanation of rebuilding a binary tree from inorder and postorder traversals using recursion and an index map.
LeetCode 105: Construct Binary Tree from Preorder and Inorder Traversal
A clear explanation of rebuilding a binary tree from preorder and inorder traversals using recursion and an index map.
LeetCode 104: Maximum Depth of Binary Tree
A clear explanation of finding the maximum depth of a binary tree using recursive depth-first search.
LeetCode 103: Binary Tree Zigzag Level Order Traversal
A clear explanation of zigzag level order traversal using breadth-first search and alternating level direction.
LeetCode 102: Binary Tree Level Order Traversal
A clear explanation of binary tree level order traversal using breadth-first search and a queue.
LeetCode 101: Symmetric Tree
A clear explanation of checking whether a binary tree is symmetric using mirror recursion.