8,9,10TIL，13wa 求教

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

struct road
{
    int a,b;
    int w;
};

int find(vector<int> p, int x)
{
    if(x != p[x])
    {
        x = find(p,p[x]);
    }
    return x;
}

bool cmp(road a, road b)
{
    return a.w < b.w;
}

int main()
{
    long long n,m;
    cin >> n >> m;
    vector<road> G(m);
    for (int i = 0; i < m; i++)
    {
        cin >> G[i].a >> G[i].b >> G[i].w;
    }

    sort(G.begin(),G.end(),cmp);

    vector<int> p(n+1);
    for (int i = 1; i < n+1; i++)
    {
        p[i] = i;
    }
    int sum = 0;
    for (int i = 0; i < m; i++)
    {
        int a = G[i].a,b = G[i].b,w = G[i].w;
        int fa = find(p,a), fb = find(p,b);
        if(fa != fb)
        {
            p[fa] = fb;
            sum += w;
        }
    }
    cout << sum;
    return 0;
}