题目链接:http://codeforces.com/contest/699/problem/D D. Fix a Tree time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A tree is an undirected connected graph without cycles. Let's consider a root…

D. Fix a Tree time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A tree is an undirected connected graph without cycles. Let's consider a rooted undirected tree with n vertices, numbered 1 th…

D. Fix a Tree time limit per test 2 seconds memory limit per test 256 megabytes     A tree is an undirected connected graph without cycles. Let's consider a rooted undirected tree with n vertices, numbered 1 through n. There are many ways to represen…

题目链接:http://codeforces.com/problemset/problem/698/B题意:告诉你n个节点当前的父节点,修改最少的点的父节点使之变成一棵有根树.思路:拆环.题解:http://codeforces.com/blog/entry/46148代码: #include <cstdio> ; int f[maxn], vis[maxn], n, s, cnt, idx; int Find(int x) { vis[x] = ++ idx; while (!vis[ f[…

B. Coach 题目连接: http://www.codeforces.com/contest/300/problem/A Description A programming coach has n students to teach. We know that n is divisible by 3. Let's assume that all students are numbered from 1 to n, inclusive. Before the university progra…

题目链接: http://codeforces.com/problemset/problem/650/C C. Table Compression time limit per test4 secondsmemory limit per test256 megabytes 问题描述 Little Petya is now fond of data compression algorithms. He has already studied gz, bz, zip algorithms and m…

F. Polycarp and Hay 题目连接: http://www.codeforces.com/contest/659/problem/F Description The farmer Polycarp has a warehouse with hay, which can be represented as an n × m rectangular table, where n is the number of rows, and m is the number of columns…

http://codeforces.com/contest/723/problem/D 这题是只能把小河填了,题目那里有写,其实如果读懂题这题是挺简单的,预处理出每一块的大小,排好序,从小到大填就行了. 以前找这些块的个数用的是dfs.现在这次用并查集做下. 首先要解决的是,二维坐标怎么并查集,以前的并查集都是一维的,现在是两个参数,那么就考虑离散,每对应一个点,离散到一个独特的一维数值即可.我用的公式的50 * x + y.这样得到的数值是唯一的.所以可以快乐地并查集了. 那么遇到一个'.',…

链接: https://codeforces.com/contest/1263/problem/D 题意: One unknown hacker wants to get the admin's password of AtForces testing system, to get problems from the next contest. To achieve that, he sneaked into the administrator's office and stole a piec…

D. Dividing Kingdom II   Long time ago, there was a great kingdom and it was being ruled by The Great Arya and Pari The Great. These two had some problems about the numbers they like, so they decided to divide the great kingdom between themselves. Th…