7-10 公路村村通(并查集kruskal)

6 15
1 2 5
1 3 3
1 4 7
1 5 4
1 6 2
2 3 4
2 4 6
2 5 2
2 6 6
3 4 6
3 5 1
3 6 1
4 5 10
4 6 8
5 6 3

12

#include<bits/stdc++.h>
#define x first
#define y second
using namespace std;
typedef long long ll;
const int N = 1e3 + 10;
const int M = 3 * N;
const int INF = 0x3f3f3f3f;
typedef pair<int,int> PII;
struct Edge{ 
   
    int u,v,w;
    bool operator<(const Edge &edge)const{ 
   
        return w < edge.w;
    }
}edge[M];
int fa[N],n,m;
void init(){ 
   
    for(int i = 0;i < n;i ++)fa[i] = i;
}
int Find(int x){ 
   
    return fa[x] = (x == fa[x] ? x : Find(fa[x]));	//压缩路径并查集
}
int main(){ 
   
    cin>>n>>m;
    init();
    int x,y,w;
    for(int i = 0;i < m;i ++){ 
   
        cin>>x>>y>>w;
        edge[i].u = x;
        edge[i].v = y;
        edge[i].w = w;
    }
    sort(edge,edge + m);
    int res = 0,cnt = 0;
    for(int i = 0;i < m;i ++){ 
   
        int X = Find(edge[i].u),Y = Find(edge[i].v);
        if(X != Y){ 
   
            fa[X] = Y;
            res += edge[i].w;
            cnt ++;
        }
    }
    if(cnt != n - 1)cout<< -1;
    else cout<<res;
    return 0;
}