POJ

直接Kruskal

但是注意一点的是 从起点到终点 

只要起点和终点连通就可以停止添加路径了 因为再添加 就会减小weight最小的路

#include <iostream>
#include <stdio.h>
#include <string>
#include <string.h>
#include <map>
#include <queue>
#include <fstream>
#include <algorithm>
#include <string.h>
#define READ() freopen("in.txt", "r", stdin);
#define MAXV 1007
#define MAXE 1000007

using namespace std;

struct Edge
{
    int from, to, cost;
    Edge () {}
    Edge (int from, int to, int cost) : from(from), to(to), cost(cost) {}
}edge[MAXE];
int num = 0;
void Add(int from, int to, int cost)
{
    edge[num++] = Edge(from, to, cost);
}
int par[MAXV];
int find(int x)
{
    if (x == par[x]) return x;
    else return par[x] = find(par[x]);
}
void unite(int x, int y)
{
    int px = find(x), py = find(y);
    if (px == py) return ;
    else par[py] = px;
}
bool same(int x, int y)
{
    int px = find(x), py = find(y);
    return px == py;
}

bool cmp(Edge e1, Edge e2)
{
    return e1.cost > e2.cost;
}

int dist[MAXE];
int n, m;
int Kruskal()
{
    int n1 = 0;
    sort(edge, edge+num, cmp);
    for (int i = 0; i < num; i++)
    {
        Edge e = edge[i];
        if (!same(e.from, e.to))
        {
            unite(e.from, e.to);
            dist[n1++] = e.cost;
        }
        if (same(1, n)) break;
    }
    sort(dist, dist+n1);
    return dist[0];
}
int main()
{
    READ()
    int T,cnt = 1;
    scanf("%d", &T);
    while (T--)
    {
        scanf("%d%d", &n, &m);
        for (int i = 1;i <= n; i++) par[i] = i;
        memset(edge, 0, sizeof(edge));
        for (int i = 0; i < m; i++)
        {
            int from, to, cost;
            scanf("%d%d%d", &from, &to, &cost);
            Add(from, to, cost);
            Add(to, from, cost);
        }
        int ans = Kruskal();
        printf("Scenario #%d:
%d

", cnt++, ans);
    }
}