【题解】ACOJ12194|BZOJ1682|USACO2005 Mar|干草危机

最小生成树板子

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
struct edge{
	int u, v, w;
}graph[20005];

inline int read()
{
	int x = 0,f = 1;char ch = getchar();
	while(ch < '0' || ch > '9'){if(ch == '-')f = -1;ch = getchar();}
	while(ch >= '0' && ch <= '9'){x = x * 10 + ch - '0';ch = getchar();}
	return x * f;
}

int n, m, tot;
int fa[2005];

bool cmp(edge a, edge b){
    return a.w < b.w;
}
int find(int x){
	if(x == fa[x]) return x;
	return fa[x] = find(fa[x]);
}

int main(){
	n = read();m = read();
	for(int i = 1;i <= n;i ++)	fa[i] = i;
	for(int i = 1;i <= m;i ++)	graph[i].u = read(), graph[i].v = read(), graph[i].w = read();
	sort(graph + 1, graph + m + 1, cmp);
	for(int i = 1;;i ++){
		int p = find(graph[i].u), q = find(graph[i].v);
		if(p != q)
		{
			fa[p] = q;tot ++;
			if(tot == n - 1)
			{
				cout << graph[i].w;
				break;
			}
		}
	}
	return 0;
}