51Nod 1212 无向图最小生成树

//克鲁斯卡尔
#include <iostream>
#include <algorithm>

using namespace std;
const int maxn = 50000 + 5;

struct node{
    int x, y;
    int len;
}g[maxn];

bool cmp(node x, node  y){
    return x.len < y.len;
}

int fa[maxn];

int Find(int x){
    if (x == fa[x])
        return x;
    else
        return fa[x] = Find(fa[x]);
}


int main(){
    ios::sync_with_stdio(false);

    int n, m;
    cin >> n >> m;
    for (int i = 0; i <= n; i++){
        fa[i] = i;
    }

    int a, b, c;
    for (int i = 0; i < m; i++){
        cin >> a >> b >> c;
        g[i].x = a;
        g[i].y = b;
        g[i].len = c;
    }
    int ans = 0;
    sort(g, g + m, cmp);
    for (int i = 0; i < m; i++){
        int u, v;
        u = g[i].x;
        v = g[i].y;
        int u1 = Find(u);
        int v1 = Find(v);
        if (u1 != v1){
            fa[v1] = u1;
            ans += g[i].len;
        }
    }
    cout << ans << endl;
    return 0;
}