题意 1-n排列,构成一个圆:1-n每个点有个值0或者1,0代表点的度为偶数,1代表点的度为计数:询问能否构成一棵树,树的连边在圆内不会相交,在圆边上可以相交,可以则输出方案. 提示 1. 首先考虑什么时候无解,显然,奇数点个数是偶数,并且>=2 2. 由奇数点个数为偶数可以发现,它们可以连到同一个偶数点上(并非直接连) 3. 剩下的偶数点可以直接顺时针串联,直到连到最近的一个奇数点上 4. 相当于每个奇数点后面有一条偶数链,或者没有偶数链只有一个奇点(这都是一样的,因为链最后一个点都只剩下一个…

time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Connected undirected weighted graph without self-loops and multiple edges is given. Graph contains n vertices and m edges. For each edge (u,…

time limit per test2 seconds memory limit per test256 megabytes inputstandard input outputstandard output A group of n cities is connected by a network of roads. There is an undirected road between every pair of cities, so there are roads in total. I…

题意: 构造题,节点1~n顺时针排列成圆形,告诉你每个点度数奇偶性,让你构造一棵树,树边不相交. 思路: 因为每条边给总度数贡献2,因此如果度数为1的点有奇数个,直接输出no.显然0个度数为1的,也输出no. 找到每个1,把1往后的部分分到一组,第二组的最后一个连第一组的最后一个,然后3组往后的最后一个连第一组的第一个(1). code: #include<bits/stdc++.h> using namespace std; const int N=1e6+5; char s[N]; int…

E. Minimum spanning tree for each edge 题目连接: http://www.codeforces.com/contest/609/problem/E Description Connected undirected weighted graph without self-loops and multiple edges is given. Graph contains n vertices and m edges. For each edge (u, v) f…

E. Minimum spanning tree for each edge 题目连接: http://www.codeforces.com/contest/609/problem/E Description Connected undirected weighted graph without self-loops and multiple edges is given. Graph contains n vertices and m edges. For each edge (u, v) f…

E. Minimum spanning tree for each edge   Connected undirected weighted graph without self-loops and multiple edges is given. Graph contains n vertices and m edges. For each edge (u, v) find the minimal possible weight of the spanning tree that contai…

E. Minimum spanning tree for each edge time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Connected undirected weighted graph without self-loops and multiple edges is given. Graph contains n …

这题本来是想放在educational round 3的题解里的,但觉得很有意思就单独拿出来写了 题目链接:609E - Minimum spanning tree for each edge 题目大意:n个点,m条边,对每条边,询问包含此边的最小生成树的边权之和 题解:大部分人都是用LCA写的,这里提供一个更为精妙的做法. 模拟Kruskal算法建MST的过程,先将m条边按边权排序,依次进行判断.若点对(u,v)属于同一个连通块,则加入边{u,v,w}后会形成一个环,把环中最大的边换成w会多产…

E. Minimum spanning tree for each edge time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Connected undirected weighted graph without self-loops and multiple edges is given. Graph contains n …