HDU 1863

http://acm.hdu.edu.cn/showproblem.php?pid=1863

复习考研练练写Prim,第一次写,乱搞的,有点难看

邻接表+堆

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>

using namespace std;

int n, m, cnt, ct, head[105], vis[105];

struct Edge {
    int s, t, v, next;
    friend bool operator < (Edge a, Edge b) {
        return a.v > b.v;
    }
}e[10005];

void add(int s, int t, int v) {
    e[cnt].t = t; e[cnt].v = v; e[cnt].next = head[s]; head[s] = cnt++;
}

int Prim() {
    int res = 0;
    priority_queue <Edge> q;
    vis[1] = 1;
    ct++;
    for(int i = head[1]; i != -1; i = e[i].next) {
        q.push(e[i]);
    }
    while(!q.empty()) {
        Edge e1 = q.top();
        q.pop();
        vis[e1.t] = 1;
        res += e1.v;
        ct++;
        if(ct == m) return res;
        for(int i = head[e1.t]; i != -1; i = e[i].next) {
            if(!vis[e[i].t]) q.push(e[i]);
        }
    }
    return -1;
} 

int main() {
    while(~scanf("%d%d", &n, &m), n) {
        cnt = ct = 0;
        memset(head, -1, sizeof(head));
        memset(vis, 0, sizeof(vis));
        for(int i = 0; i < n; i++) {
            int s, t, v;
            scanf("%d%d%d", &s, &t, &v);
            add(s, t, v);
        }
        int ans = Prim();
        if(ans == -1) puts("?");
        else printf("%d\n", ans);
    }
    return 0;
}