Tree

LeetCode 1080: Insufficient Nodes in Root to Leaf Paths

A clear explanation of pruning tree nodes where all root-to-leaf paths through them have sum less than a limit, using post-order DFS.

LeetCode 1038: Binary Search Tree to Greater Sum Tree

A clear explanation of converting a BST to a greater sum tree by accumulating values in reverse inorder traversal.

LeetCode 1028: Recover a Tree From Preorder Traversal

A clear explanation of reconstructing a binary tree from a depth-encoded preorder traversal string using a stack.

LeetCode 1026: Maximum Difference Between Node and Ancestor

A clear explanation of finding the maximum ancestor-node difference in a binary tree by tracking min and max along each root-to-leaf path.

LeetCode 1022: Sum of Root To Leaf Binary Numbers

A clear explanation of summing root-to-leaf binary numbers in a binary tree using DFS with accumulated values.

LeetCode 1008: Construct Binary Search Tree from Preorder Traversal

A clear explanation of reconstructing a BST from its preorder traversal using value range bounds.

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 617: Merge Two Binary Trees

A recursive tree traversal guide for merging two binary trees node by node.

LeetCode 582: Kill Process

A clear graph traversal solution for finding all processes terminated when killing a target process.

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 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 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 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 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 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 145: Binary Tree Postorder Traversal

Return the postorder traversal of a binary tree using recursion or an iterative stack-based approach.

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 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 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 971: Flip Binary Tree To Match Preorder Traversal

A clear explanation of matching a binary tree preorder traversal by greedily flipping nodes.

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 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 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 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 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 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 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 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 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 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 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 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 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 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.