HDU 1301 Jungle Roads

最小生成树prim

 原理参见上篇

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;

const int INF = 99999999 ;
const int maxn = 105 ;

int map[maxn][maxn];
int visit[maxn];
int low[maxn];

int main (){
    int n;
    while (~scanf ("%d",&n)&&n){
        for (int i=0;i<n;i++)
            for (int j=0;j<n;j++)
                map[i][j]=INF;
        for (int i=0;i<n-1;i++){
            char c[10];
            int a,b;
            scanf ("%s%d",c,&a);
            while (a--){
                scanf ("%s%d",c,&b);
                map[i][(int)(c[0]-'A')]=map[(int)(c[0]-'A')][i]=b;
            }//cout<<n<<" "<<i<<endl;
        }
        memset (visit,0,sizeof visit);
        int ans=0;
        int mi;
        int pos=1;
        visit[1]=1;
        for (int i=0;i<n;i++)
            low[i]=map[pos][i];
        for (int i=0;i<n-1;i++){
            mi=INF;
            for (int j=0;j<n;j++)
                if (!visit[j]&&low[j]<mi){
                    mi=low[j];pos=j;
                }
            ans+=mi;visit[pos]=1;
            for (int j=0;j<n;j++)
                if (!visit[j])
                    low[j]=min (low[j],map[pos][j]);
        }
        printf ("%d
",ans);
    }
    return 0;
}