图论 - 数论 - 生成树

题目链接：https://www.luogu.org/problem/P3366

代码：

#include <bits/stdc++.h>

using namespace std;

const int N = 5010;

const int M = 200010;

int n, m, dis[N], ans;

int tot, head[N], val[M << 1], nxt[M << 1] ,to[M << 1];

bool vis[N];

void add(int x, int y, int z) {
    to[ ++ tot] = y;
    val[tot] = z;
    nxt[tot] = head[x];
    head[x] = tot;
}

void Prim() {
    memset(dis, 0x3f, sizeof dis);
    memset(vis, 0, sizeof vis);
    dis[1] = 0;
    for (int i = 1; i <= n; i ++ ) {
        int tmp = 1 << 30, k;
        for (int j = 1; j <= n; j ++ ) {
            if (vis[j] == 0 && dis[j] < tmp) {
                tmp = dis[j];
                k = j;
            }
        }
        vis[k] = 1;
        ans += dis[k];
        for (int j = head[k]; j; j = nxt[j]) {
            if (vis[to[j]] == 0 && dis[to[j]] > val[j]) {
                dis[to[j]] = val[j];
            }
        }
    }
}

int main() {
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= m; i ++ ) {
        int x, y, z;
        scanf("%d%d%d", &x, &y, &z);
        add(x, y, z);
        add(y, x, z);
    }
    Prim();
    printf("%d\n", ans);
    return 0;
}

原文地址：https://www.cnblogs.com/littleseven777/p/11857174.html