对于每条河流,要让它排名最靠前,那么显然它必须要延伸到根. 设第$i$条河流到根的距离为$d[i]$,对于每个节点,如果存在一条河流比$d[i]$长,那么让它延伸会使答案最小,否则要选择一条最短的河流来进行延伸. 设$f[i]$表示每个节点往外延伸的河流的长度的最小值,可以通过树形DP求出. 从小到大考虑每个$d$,取出所有超过了上一个$d$的限制,但是满足当前的$d$限制的临界点,这些点将不再是临界点. 若一个点所有的儿子都不是临界点,那么它的将变为临界点. 用堆按$f$从小到大维护临界点即可…

Search GO 说明:输入题号直接进入相应题目,如需搜索含数字的题目,请在关键词前加单引号 Problem ID Title Source AC Submit Y 1000 A+B Problem 10983 18765 Y 1036 [ZJOI2008]树的统计Count 5293 13132 Y 1588 [HNOI2002]营业额统计 5056 13607 1001 [BeiJing2006]狼抓兔子 4526 18386 Y 2002 [Hnoi2010]Bounce 弹飞绵羊 43…

题目描述 Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest…

题目描述 Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring. 即给定一个字符串,求它的最长回文子串的长度(或者最长回文子串). 解法一 对于一个问题,一定可以找到一个傻的可爱的暴力解法,本题的暴力解法即…

Find the length of the longest substring T of a given string (consists of lowercase letters only) such that every character in T appears no less than k times. Example 1: Input: s = "aaabb", k = 3 Output: 3 The longest substring is "aaa"…

题目来自 https://leetcode.com/problems/longest-palindromic-substring/ 题目:Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring. 给一个字符串…

Given a string that consists of only uppercase English letters, you can replace any letter in the string with another letter at most k times. Find the length of a longest substring containing all repeating letters you can get after performing the abo…

Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters. This is case sensitive, for example "Aa" is not considered a palindrome here. Note: Assume the leng…

Suppose we abstract our file system by a string in the following manner: The string "dir\n\tsubdir1\n\tsubdir2\n\t\tfile.ext" represents: dir subdir1 subdir2 file.ext The directory dir contains an empty sub-directory subdir1 and a sub-directory …

Given a string, find the length of the longest substring T that contains at most k distinct characters. For example, Given s = “eceba” and k = 2, T is "ece" which its length is 3. 这道题是之前那道Longest Substring with At Most Two Distinct Characters的拓展…