最小生成树 : 虚拟源点

https://www.acwing.com/problem/content/1148/

#include <bits/stdc++.h>
using namespace std;
#define IO ios::sync_with_stdio(false);cin.tie(0); cout.tie(0)
inline int lowbit(int x) { return x & (-x); }
#define ll long long
#define pb push_back
#define PII pair<int, int>
#define x first
#define y second
#define inf 0x3f3f3f3f
const int N = 310;
int n;
int w[N][N];
int dist[N];
bool st[N];

int prim() {
    memset(dist, 0x3f, sizeof dist);
    dist[0] = 0;
    int res = 0;
    for (int i = 0; i < n + 1; ++i) {
        int t = -1;
        for (int j = 0; j <= n; ++j)
            if (!st[j] && (t == -1 || dist[j] < dist[t]))
                t = j;
        st[t] = true;
        res += dist[t];
        for (int j = 0; j <= n; ++j) dist[j] = min(dist[j], w[t][j]);
    }
    return res;
}


int main() {
    IO;
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        cin >> w[0][i];
        w[i][0] = w[0][i];
    }
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= n; ++j)
            cin >> w[i][j];
    cout << prim() << '\n';
    return 0;
}