c++编写prim算法

以下是C++编写prim算法的示例代码：

#include <iostream>
#include <vector>
#include <queue>
#include <cstring>
using namespace std;

const int MAXN = 1005;
const int INF = 0x3f3f3f3f;

struct Edge {
    int to, w;
    Edge(int to, int w) : to(to), w(w) {}
};

vector<Edge> G[MAXN];
int d[MAXN];
bool vis[MAXN];

void prim(int s) {
    memset(d, INF, sizeof(d));
    memset(vis, false, sizeof(vis));
    d[s] = 0;
    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> q;
    q.push(make_pair(0, s));
    while (!q.empty()) {
        int u = q.top().second;
        q.pop();
        if (vis[u]) continue;
        vis[u] = true;
        for (int i = 0; i < G[u].size(); i++) {
            int v = G[u][i].to;
            int w = G[u][i].w;
            if (!vis[v] && w < d[v]) {
                d[v] = w;
                q.push(make_pair(d[v], v));
            }
        }
    }
}

int main() {
    int n, m;
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        G[u].push_back(Edge(v, w));
        G[v].push_back(Edge(u, w));
    }
    prim(1);
    int ans = 0;
    for (int i = 1; i <= n; i++) {
        if (d[i] == INF) {
            cout << "No Answer" << endl;
            return 0;
        }
        ans += d[i];
    }
    cout << ans << endl;
    return 0;
}