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摘要： 2246. Longest Path With Different Adjacent Characters Hard You are given a tree (i.e. a connected, undirected graph that has no cycles) rooted at node 阅读全文

摘要： 864. Shortest Path to Get All Keys You are given an m x n grid grid where: '.' is an empty cell. '#' is a wall. '@' is the starting point. Lowercase l 阅读全文

摘要： csrf 攻击的预防： 1.敏感操作api尽量不使用get请求，原因：容易伪造 2.验证码二次验证，用户发送请求时，要求短信验证码验证，确保是人为操作 3.检查refer，浏览器发送请求到服务端的时候，会带上refer 字段（请求来自哪个url），如果refer传过来的domain和当前网站不同，那 阅读全文

摘要： 62. Unique Paths Medium There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0]). The robot tries t 阅读全文

摘要： 1726. Tuple with Same Product Medium 47322Add to ListShare Given an array nums of distinct positive integers, return the number of tuples (a, b, c, d) 阅读全文

摘要： 2370. Longest Ideal Subsequence Medium You are given a string s consisting of lowercase letters and an integer k. We call a string t ideal if the foll 阅读全文

摘要： 516. Longest Palindromic Subsequence Medium Given a string s, find the longest palindromic subsequence's length in s. A subsequence is a sequence that 阅读全文

摘要： 907. Sum of Subarray Minimums Medium Given an array of integers arr, find the sum of min(b), where b ranges over every (contiguous) subarray of arr. S 阅读全文

摘要： 300. Longest Increasing Subsequence Medium Given an integer array nums, return the length of the longest strictly increasing subsequence. A subsequenc 阅读全文

摘要： 01背包 假设有4个背包(weight,contribute)，(2,1),(3,3),(4,5),(7,9) 总重量:totalWeight = 10, 在不超过totalWeight的情况下如何使得contribute最大？每个背包最多只能使用一次 下面 i 表示前 i 个背包可选，j 表示to 阅读全文