python/TangDou/AcWing/MinimalSpanningTree/1141_Prim.cpp

#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;

const int N = 110;
int w[N][N];
int dist[N];
bool st[N];
int n, m, sum;
int b[N];

int prim(int source) {
    memset(dist, 0x3f, sizeof dist);
    dist[source] = 0;
    b[source] = 1;

    int res = 0;
    for (int i = 1; i <= n; i++) {
        int t = -1;
        for (int j = 1; j <= n; j++)
            if (!st[j] && (t == -1 || dist[t] > dist[j]))
                t = j;
        st[t] = true;

        if (dist[t] != INF) res += dist[t], b[t] = 1;
        for (int j = 1; j <= n; j++)
            dist[j] = min(dist[j], w[t][j]);
    }
    return res;
}

int main() {
    cin >> n >> m;
    memset(w, 0x3f, sizeof w);
    while (m--) {
        int a, b, c;
        cin >> a >> b >> c;
        w[a][b] = w[b][a] = c;
        sum += c; // 总边长
    }

    int s = 0;
    for (int i = 1; i <= n; i++)
        if (!b[i]) s += prim(i);

    printf("%d\n", sum - s);
    return 0;
}