leetcode 解题思路

Given therootof a binary tree, find the maximum average value of any subtree of that tree.(A subtree of a tree is any node of that tree plus all its descendants. The average value of a tree is the sum of its values, divided by the number of nodes.)Ex..

Given a binary tree, find the maximum path sum.The path may start and end at any node in the tree.For example:Given the below binary tree, 1 / \ 2 3Return 6.思路： 主要看

You are given a binary tree in which each node contains an integer value.Find the number of paths that sum to a given value.The path does not need to start or end at the root or a leaf, but it ...

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.For example:Given the below binary tree and sum =...

Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.Basically, the deletion can be divided ...

Given a binary tree, collect a tree's nodes as if you were doing this: Collect and remove all leaves, repeat until the tree is empty.Example:Given binary tree 1 / \ ...

Input: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]Output: 5思路：BFS level order/*// Definition for a Node.class Node { public int val...

Given two non-empty binary treessandt, check whether treethas exactly the same structure and node values with a subtree ofs. A subtree ofsis a tree consists of a node insand all of this node...

Given therootof a binary tree and an integerdistance. A pair of two differentleafnodes of a binary tree is said to be good if the length ofthe shortest pathbetween them is less than or equal todistance.Returnthe number of good leaf node pairsin...

Tree的traverse，Preorder, Inorder, Postorder ，这些都是用stack来模拟考察的比较多。参考这里：PreOrder, InOrder, PostOrder 题型总结这里主要总结，divide and conquer 逻辑，往上返回result的情况；Lowest Common Ancestor of a Binary Search TreeLowest Common Ancestor of a Binary TreeClosest Binary S..

Given therootof a binary tree withNnodes, eachnodein the tree hasnode.valcoins, and there areNcoins total.In one move, we may choose two adjacent nodes and move one coin from one node to another. (The move may be from parent to child, or from ...

Afull binary treeis a binary tree where each node has exactly 0 or 2children.Return a list of all possible full binary trees withNnodes. Each element of the answer is the root node of one possible tree.Eachnodeof eachtree in the answermustha...

Given a binary tree, you need to find the length of Longest Consecutive Path in Binary Tree.Especially, this path can be either increasing or decreasing. For example, [1,2,3,4] and [4,3,2,1] are both considered valid, but the path [1,2,4,3] is not valid.

Given a binary tree, find the largest subtree which is a Binary Search Tree (BST), where largest means subtree with largest number of nodes in it.Note:A subtree must include all of its descendan

Givenn, generate all structurally uniqueBST's(binary search trees) that store values 1...n.For example,Givenn= 3, your program should return all 5 unique BST's shown below. 1 3

Given a binary tree rooted atroot, thedepthof each node is the shortest distance to the root.A node isdeepestif it has the largest depth possible amongany node in theentire tree.The subtree of a node is that node, plus the set of all descendants...

Given a Binary Search Tree (BST) with root noderoot, and a target valueV, split the tree into two subtreeswhere one subtree has nodes that are all smaller or equal to the target value, while the other subtree has all nodes that are greater than the targ...

Given a binary search tree and the lowest and highest boundaries asLandR, trim the tree so that all its elements lies in[L, R](R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary se...

Given a binary search tree and the lowest and highest boundaries asLandR, trim the tree so that all its elements lies in[L, R](R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary se...

Given a binary treerootand an integertarget, delete all theleaf nodeswith valuetarget.Notethat once you delete a leaf node with valuetarget,if it's parent node becomes a leaf node and has t...

Given a non-empty special binary tree consisting of nodes with the non-negative value, where each node in this tree has exactlytwoorzerosub-node. If the node has two sub-nodes, then this node's va...

Given therootnode of a binary search tree, return the sum of values of all nodes with value betweenLandR(inclusive).The binary search tree is guaranteed to have unique values.Example 1:...

Given therootof a binary tree, each node in the tree has a distinct value.After deletingall nodes with a value into_delete, we are left with a forest (adisjoint union of trees).Return the roo...

Given a binary tree where all the right nodes are either leaf nodes with a sibling (a left node that shares the same parent node) or empty, flip it upside down and turn it into a tree where the origin...

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Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.思路：recursion:左边为空的时候，只返回右边的+1，右...

The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After a tour...

Mergeksorted linked lists and return it as one sorted list.Analyze and describe its complexity.ExampleExample 1: Input: [2->4->null,null,-1->null] Output: -1->2->4->nul...

Givenksorted integer arrays, merge them into one sorted array.ExampleExample 1:Input: [ [1, 3, 5, 7], [2, 4, 6], [0, 8, 9, 10, 11] ]Output: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10...

Given the root and two nodes in a Binary Tree. Find the lowest common ancestor(LCA) of the two nodes.The lowest common ancestor is the node with largest depth which is the ancestor of both nodes.Ret...

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes ...

Flatten a binary tree to a fake "linked list" in pre-order traversal.Here we use therightpointer in TreeNode as thenextpointer in ListNode.ExampleExample 1:Input:{1,2,5,3,4,#,6}Output：{1...

Given a binary tree, return all root-to-leaf paths.For example, given the following binary tree: 1 / \2 3 \ 5All root-to-leaf paths are:["1->2->5", "1->3"]思...

Given a binary tree, find the subtree with minimum sum. Return the root of the subtree.ExampleExample 1:Input:{1,-5,2,1,2,-4,-5}Output:1Explanation:The tree is look like this: 1 / ...