Ice_cream’s world III//最小生成树kruskal

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
const int size = 1e4 + 1;
struct edge
{
    int a, b, c;
};
struct edge edges[size];
int un[size];

int cmp(edge x, edge y)
{
    return x.c < y.c;
}

int find(int x)
{
    if(x == un[x])
        return x;
    return find(un[x]);
}

void Union(int x, int y)
{
    int c1 = find(x);
    int c2 = find(y);
    un[c1] = c2;
}

int main()
{
    int N, M;
    int S, T, C;
    while(cin >> N >> M)
    {
        for(int i = 0; i < N; i++)
            un[i] = i;

        for(int i = 0; i < M; i++)
        {
            cin >> edges[i].a >> edges[i].b >> edges[i].c;
        }
        sort(edges, edges+M, cmp);
        int count = N;
        int ans = 0;
        for(int i = 0; i < M; i++)
        {
            if(find(edges[i].a) == find(edges[i].b))
                continue;
            Union(edges[i].a, edges[i].b);
            count--;
            ans+=edges[i].c;
        }
        if(count != 1)
        {
            printf("impossible\n\n");
            continue;
        }
        printf("%d\n\n", ans);
    }
    return 0;
}