题目大意:给定一个 N 个点的无向图,点有点权,求从 0 号点走到 N-1 号点的最短哈密顿路径是多少. 题解:由于哈密顿路径的定义是每个顶点必须经过且仅能经过一次,因此,可用当前是否经过了这些点和当前在哪个点来表示出一个状态,则一共有 \(O(n2^n)\) 个状态.考虑转移方式,对于在 j 这个点的情况来说,可以从以下与 j 相邻的节点 k 转移来,k 必须满足在当前状态已经走到.因此,时间复杂度为 \(O(n^22^n)\). update at 2019.3.29 注意,由于状态转移方程…

题目链接:http://acm.timus.ru/problem.aspx?space=1&num=1143 题意:逆时针给一个凸包的n(n<=200)个顶点坐标,求一个最短哈密顿路径的长度. 解法:求最短哈密顿本身是一个NP问题,可是由于是凸包上,能够利用这个做:有一个性质:凸包上的最短哈密顿路径不会出现交叉.所以能够看出来从一点出发,他要么和顺时针相邻点连接,要么和逆时针相邻点相连接.通过这个性质能够通过dp做: ans[i][j][0]表示i開始.往后j的点最短路径长度,ans[i][…

虐狗宝典学习笔记: 取出整数\(n\)在二进制表示下的第\(k\)位                                                    \((n >> k) & 1)\) 取出整数\(n\)在二进制表示下的第\(0 ~ k - 1\)位(后\(k\)位)                    \(n & ((1 << k) - 1)\) 把整数\(n\)在二进制表示下的第\(k\)位取反                     …

正解:状压dp 解题报告: 完了吃枣退役:D 我是真的没想到这是个dp...脑子越来越不好了,大概是太久没碰OI了都要生疏了...哭了,感觉自己太傻逼了可能不适合学信息... 知道是个状压dp就easy了鸭直接f[i][j]表示状态i在j点地转移就好了,没有太多可以说了的? 实在没有技术含量呢,但就是想不到,真的太傻逼,烦躁了 大概还是基础不够扎实呢,多刷题趴先qwq #include<bits/stdc++.h> using namespace std; #define ll long lo…

A string such as "word" contains the following abbreviations: ["word", "1ord", "w1rd", "wo1d", "wor1", "2rd", "w2d", "wo2", "1o1d", "1or1", "…

This is a follow up of Shortest Word Distance. The only difference is now word1 could be the same as word2. Given a list of words and two words word1 and word2, return the shortest distance between these two words in the list. word1 and word2 may be…

This is a follow up of Shortest Word Distance. The only difference is now you are given the list of words and your method will be called repeatedly many times with different parameters. How would you optimize it? Design a class which receives a list…

Given a string S, you are allowed to convert it to a palindrome by adding characters in front of it. Find and return the shortest palindrome you can find by performing this transformation. For example: Given "aacecaaa", return "aaacecaaa&qu…

Given an array of n positive integers and a positive integer s, find the minimal length of a subarray of which the sum ≥ s. If there isn't one, return 0 instead. For example, given the array [2,3,1,2,4,3] and s = 7,the subarray [4,3] has the minimal…

最短匹配应用于:假如有一段文本,你只想匹配最短的可能,而不是最长. 例子 比如有一段html片段,'\this is first label\\the second label\',如何匹配出每个a标签中的内容,下面来看下最短与最长的区别. 代码 >>> import re >>> str = '<a>this is first label</a><a>the second label</a>' >>>…