poj 1258 Agri-Net

点击打开链接poj 258

思路：最小生成树 + prime

代码：

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
using namespace std;
#define MAXN 110
#define INF 0XFFFFFFF

int n;
int vis[MAXN];
int lowcost[MAXN];
int G[MAXN][MAXN];

void init(){
    memset(vis , 0 , sizeof(vis));
    memset(lowcost , 0 , sizeof(lowcost));
    for(int i = 1 ; i <= n ; i++){
       for(int j = 1 ; j <= n ; j++)
           G[i][j] = INF;
    } 
}

void prime(){
     int pos , ans;
     ans = 0;
     vis[1] = 1;
     for(int i = 1 ; i <= n ; i++)
        lowcost[i] = G[1][i];
     for(int i = 1 ; i <= n ; i++){
        pos = -1;
        for(int j = 1 ; j <= n ; j++){
           if(!vis[j] && (pos == -1 || lowcost[j] < lowcost[pos]))
             pos = j;
        }
        if(pos == -1)
            break;
        ans += lowcost[pos];
        vis[pos] = 1;
        for(int j = 1 ; j <= n ; j++){
           if(!vis[j] && lowcost[j] > G[j][pos])
             lowcost[j] = G[j][pos];
        }
     }
     printf("%d\n" , ans);
}

int main(){
    int tmp;
    while(scanf("%d" , &n) != EOF){
        init();
        for(int i = 1 ; i <= n ; i++){
           for(int j = 1 ; j <= n ; j++){
               scanf("%d" , &tmp);
               if(G[i][j] > tmp)
                   G[i][j] = tmp;
           }
        }
        prime();
    }
    return 0;
}