UVaLive2515

Kruskal模板题，对着板子敲就行了

#include<iostream>
#include<cstdio>
#include<string.h>
#include<stack>
#include<set>
#include<map>
#include<vector>
#include<algorithm>
#include<cstring>
#include<queue>
using namespace std;
const int maxn = 5000005;
int p,r;
struct edge{
    int to, from, cost;
    bool operator < (const edge &p) const{
        return cost < p.cost;}
}E[maxn];
int P[50+5];

void maketree()
{
    for (int i = 0; i < 55; i++) P[i] = i;
}

int Find(int x)
{
    if (x != P[x])
        return P[x] = Find(P[x]);
    return P[x];
}

void unite(int x, int y)
{
    int p1 = Find(x);
    int p2 = Find(y);
    P[p2] = p1;
}

int main()
{
    while (scanf("%d", &p) && p)
    {
        scanf("%d", &r);
        if (r == 0){ printf("0\n");continue;}

        for (int i = 0; i < r; i++)
            scanf("%d %d %d", &E[i].to, &E[i].from, &E[i].cost);
        sort(E, E+r);
        maketree();
        int sum = 0;
        for (int i = 0; i < r; i++)
        {
            int v1 = E[i].to;
            int v2 = E[i].from;
            if (Find(v1) == Find(v2))
                continue;
            else
            {
                unite(v1, v2);
                sum += E[i].cost;
            }
        }
        printf("%d\n", sum);
    }

    return 0;
}