摘要： 216. Combination Sum III Find all valid combinations of k numbers that sum up to n such that the following conditions are true: Only numbers 1 through 阅读全文

摘要： 回溯算法理论基础 回溯法也可以叫做回溯搜索法，它是一种搜索的方式。 回溯是递归的副产品，只要有递归就会有回溯。 回溯的本质是穷举，穷举所有可能，然后选出我们想要的答案，如果想让回溯法高效一些，可以加一些剪枝的操作，但也改不了回溯法就是穷举的本质。 回溯法，一般可以解决如下几种问题： 组合问题：N个数 阅读全文

摘要： 669. Trim a Binary Search Tree Given the root of a binary search tree and the lowest and highest boundaries as low and high, trim the tree so that all 阅读全文

摘要： 235. Lowest Common Ancestor of a Binary Search Tree Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in 阅读全文

摘要： 530. Minimum Absolute Difference in BST Given the root of a Binary Search Tree (BST), return the minimum absolute difference between the values of any 阅读全文

摘要： 654. Maximum Binary Tree You are given an integer array nums with no duplicates. A maximum binary tree can be built recursively from nums using the fo 阅读全文

摘要： 513. Find Bottom Left Tree Value Given the root of a binary tree, return the leftmost value in the last row of the tree. Example 1: Input: root = [2,1 阅读全文

摘要： 110. Balanced Binary Tree Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as: a bi 阅读全文

摘要： 104. Maximum Depth of Binary Tree Given the root of a binary tree, return its maximum depth. A binary tree's maximum depth is the number of nodes alon 阅读全文

摘要： 102. Binary Tree Level Order Traversal Given the root of a binary tree, return the level order traversal of its nodes' values. (i.e., from left to rig 阅读全文