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738. Monotone Increasing Digits An integer has monotone increasing digits if and only if each pair o

435. Non-overlapping Intervals Given an array of intervals intervals where intervals[i] = [starti, e

860. Lemonade Change At a lemonade stand, each lemonade costs $5. Customers are standing in a queue

1005. Maximize Sum Of Array After K Negations Given an integer array nums and an integer k, modify t

122. Best Time to Buy and Sell Stock II You are given an integer array prices where prices[i] is the

455. Assign Cookies Assume you are an awesome parent and want to give your children some cookies. Bu

332. Reconstruct Itinerary You are given a list of airline tickets where tickets[i] = [fromi, toi] r

491. Non-decreasing Subsequences Given an integer array nums, return all the different possible non-

93. Restore IP Addresses A valid IP address consists of exactly four integers separated by single do

39. Combination Sum Given an array of distinct integers candidates and a target integer target, retu

216. Combination Sum III Find all valid combinations of k numbers that sum up to n such that the fol

题目分类 77. Combinations Given two integers n and k, return all possible combinations of k numbers chos

669. Trim a Binary Search Tree Given the root of a binary search tree and the lowest and highest bou

235. Lowest Common Ancestor of a Binary Search Tree Given a binary search tree (BST), find the lowes

530. Minimum Absolute Difference in BST Given the root of a Binary Search Tree (BST), return the min

654. Maximum Binary Tree You are given an integer array nums with no duplicates. A maximum binary tr

513. Find Bottom Left Tree Value Given the root of a binary tree, return the leftmost value in the l

110. Balanced Binary Tree Given a binary tree, determine if it is height-balanced. A height-balanced

104. Maximum Depth of Binary Tree Given the root of a binary tree, return its maximum depth. A binar

226. Invert Binary Tree Given the root of a binary tree, invert the tree, and return its root. 题目解析：