7.2 挖沟

题目链接

挖沟

代码实现

#include <bits/stdc++.h>

using namespace std;

const int N = 1e5 + 10, M = 5e5 + 10;

struct Edge
{
    int u, v, w;
    bool operator < (const Edge &W)const
    {
        return w < W.w;
    }
}edge[M];

int p[N];
int n, m;

int find(int a)
{
    if (p[a] != a) p[a] = find(p[a]);
    return p[a];
}

int Kruskal()
{
    for (int i = 1; i <= n; i ++ ) p[i] = i;

    sort(edge, edge + m);

    int res = 0, cnt = 0;

    for (int i = 0; i < m; i ++ )
    {
        auto e = edge[i];

        int pu = find(e.u), pv = find(e.v);

        if (pu != pv)
        {
            p[pv] = pu;
            res += e.w;
            cnt ++;
        }
    }
    return res;
}

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    cin >> n >> m;

    for (int i = 0; i < m; i ++ )
    {
        int a, b, c;
        cin >> a >> b >> c;
        edge[i] = {a, b, c};
    }

    int t = Kruskal();

    cout << t << endl;

    return 0;
}