Networking POJ - 1287

題目連接：https://vjudge.net/problem/POJ-1287

思路：最小生成樹板子題

 

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <stack>
#include <string>
#include <map>
#include <cmath>
#include <iomanip>
using namespace std;
 
typedef long long LL;
#define inf 1e9
#define rep(i,j,k) for(int i = (j); i <= (k); i++)
#define rep__(i,j,k) for(int i = (j); i < (k); i++)
#define per(i,j,k) for(int i = (j); i >= (k); i--)
#define per__(i,j,k) for(int i = (j); i > (k); i--)

const int N = 60;
int head[N];
int dis[N];
bool vis[N];
int cnt;
int n,m;

struct Edge{
    int to;
    int w;
    int nxt;
}e[N*N];

struct node{
    int u;
    int w;

    friend bool operator<(const node& a,const node& b){
        return a.w > b.w;
    }
};

priority_queue<node> que;

void add(int u,int v,int w){
    e[cnt].to = v;
    e[cnt].w = w;
    e[cnt].nxt = head[u];
    head[u] = cnt++;
}

int prime(){

    while(!que.empty()) que.pop();

    rep(i,1,n){
        vis[i] = false;
        dis[i] = inf;
    }
    dis[1] = 0;
    que.push(node{1,dis[1]});

    int u,v,w;
    while(!que.empty()){
        u = que.top().u;
        que.pop();
        if(vis[u]) continue;
        vis[u] = true;
        for(int o = head[u]; ~o; o = e[o].nxt){
            v = e[o].to;
            w = e[o].w;

            if(!vis[v] && dis[v] > w){
                dis[v] = w;
                que.push(node{v,dis[v]});
            }
        }
    }

    int ans = 0;
    rep(i,1,n) ans += dis[i];
    return ans;
}

int main(){

    ios::sync_with_stdio(false);
    cin.tie(0);

    int u,v,w; 
    while(cin >> n && n){
        cin >> m;
        rep(i,1,n) head[i] = -1;
        cnt = 0;

        rep(i,1,m){
            cin >> u >> v >> w;
            add(u,v,w);
            add(v,u,w);
        }
        
        cout << prime() << endl;
    }

    return 0;
}