【Kruskal】P1546 最短网络 Agri-Net

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

int fa[200010];
int n;
int cnt;

struct Edge
{
    int u, v, w;
    bool operator <(Edge s)
    {
        return w < s.w;
    }
}e[200010];

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

int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n; j++)
        {
            cin >> e[++cnt].w;
            e[cnt].u = i;
            e[cnt].v = j;
        }
    }
    sort(e + 1, e + cnt + 1);
    int sum = 0;
    int tot = 1;
    for (int i = 1; i <= cnt; i++)
    {
        fa[i] = i;
        if (find(e[i].u) != find(e[i].v))
        {
            sum += e[i].w;
            fa[find(e[i].u)] = e[i].v;
            tot++;
            if (tot >= n) break;
        }
    }
    cout << sum;
}