题目:http://codeforces.com/contest/512/problem/C 题目大意:给你若干个数,让你分成k组,每组围成一个圆,使得相邻两个数和均为素数,且每组人数应>=3个.输出方案 分析:不容易想到最大流. 官方解答: 因为每个数都>=2,所以素数一定是由一个奇数+一个偶数,即一个奇数两边的必须为偶数,一个偶数的周围的必须是奇数. 于是考虑: 若一个奇数和一个偶数的和为素数,那么在它们之间连上双向边,权值为1 因为每个奇数要连两个偶数,每个偶数要连两个奇数,所以可以弄个…

E. Fox And Dinner time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Fox Ciel is participating in a party in Prime Kingdom. There are n foxes there (include Fox Ciel). The i-th fox is ai year…

D. Fox And Jumping 题目连接: http://codeforces.com/contest/510/problem/D Description Fox Ciel is playing a game. In this game there is an infinite long tape with cells indexed by integers (positive, negative and zero). At the beginning she is standing at…

C. Fox And Names 题目连接: http://codeforces.com/contest/510/problem/C Description Fox Ciel is going to publish a paper on FOCS (Foxes Operated Computer Systems, pronounce: "Fox"). She heard a rumor: the authors list on the paper is always sorted in…

B. Fox And Two Dots 题目连接: http://codeforces.com/contest/510/problem/B Description Fox Ciel is playing a mobile puzzle game called "Two Dots". The basic levels are played on a board of size n × m cells, like this: Each cell contains a dot that ha…

A. Fox And Snake 题目连接: http://codeforces.com/contest/510/problem/A Description Fox Ciel starts to learn programming. The first task is drawing a fox! However, that turns out to be too hard for a beginner, so she decides to draw a snake instead. A sna…

题目传送门 /* DFS:每个点四处寻找,判断是否与前面的颜色相同,当走到已走过的表示成一个环 */ #include <cstdio> #include <iostream> #include <cstring> #include <string> #include <map> #include <algorithm> #include <vector> #include <set> #include <…

题目传送门 /* 水题 找规律输出 */ #include <cstdio> #include <iostream> #include <cstring> #include <string> #include <map> #include <algorithm> #include <vector> #include <set> #include <cmath> using namespace std…

题目传送门 /* 给出n个字符串,求是否有一个“字典序”使得n个字符串是从小到大排序 拓扑排序 详细解释:http://www.2cto.com/kf/201502/374966.html */ #include <cstdio> #include <iostream> #include <cstring> #include <string> #include <map> #include <algorithm> #include &…

http://codeforces.com/problemset/problem/510/B #include "cstdio" #include "cstring" int r,c; ][]; ][]; int mark; ]={,-,,},dy[]={,,,-}; int judge(int x,int y) { ||x>=r||y<||y>=c) ; ; } void dfs(int x,int y,int perX,int perY) {…