最小生成树之Prim算法+堆优化

#include<bits/stdc++.h>
#define INF 0x3f3f3f3f3f3f3f3f
#define mod 1000000007
#define IOS ios::sync_with_stdio(false)
#define endl '\n'

using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
typedef pair<int, int> p;

vector<p>vec[maxn];
int vis[maxn];
int main() {
    int n, m;
    int u, v, val;
    int ans = 0;
    scanf("%d%d", &n, &m);
    memset(vis, 0, sizeof(vis));
    for (int i = 1;i <= m;++i) {
        scanf("%d%d%d", &u, &v, &val);//读入边
        vec[u].push_back(p(val, v));//顶点u到v距离为val
        vec[v].push_back(p(val, u));//顶点v到u距离为val
    }
    priority_queue<p, vector<p>, greater<p> >pq;//优先队列
    vis[1] = 1;
    for (int i = 0;i < vec[1].size();++i) {
        pq.push(vec[1][i]);//将与1相连的顶点入队
    }
    while (!pq.empty()) {
        p now = pq.top();
        pq.pop();
        if (!vis[now.second]) {//当前顶点没有被访问过
            vis[now.second] = 1;//标记已经被访问过
            ans += now.first;
        }
        for (int i = 0;i < vec[now.second].size();++i) {//枚举与刚刚进树的这个顶点
            if (!vis[vec[now.second][i].second]) {//相邻的顶点
                pq.push(vec[now.second][i]);//将其进队列 优先队列会自动排序
            }
        }
    }
    printf("%d\n", ans);
    return 0;
}