zoj 1372

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=1372




#include<iostream>
#include<cstdio>
using namespace std;
#define N 1005
int a[N][N],low[N],n,ans;
int b[N];

int min(int x,int y)
{    return x<y?x:y;   }

void prim(int u0)
{
    int i,j,m,k;
    ans=0;
    for (i=1;i<n;i++)  low[i]=a[u0][i];
    low[u0]=-1;
    for (i=1;i<n;i++)
    {
        m=1<<20;
        for (j=0;j<n;j++)
            if (low[j]!=-1&&low[j]<m)
            {    m=low[j];    k=j;   }
        ans+=m;
        low[k]=-1;
        for (j=0;j<n;j++)
            if (low[j]!=-1)low[j]=min(low[j],a[k][j]);
    }
}

int main()
{
   int i,j,t;
   while(scanf("%d",&n)&&n)
   {
      scanf("%d",&t);
      for(i=0;i<n;i++)
       for(j=0;j<n;j++)
          a[i][j]=1<<20;
      for(i=0;i<t;i++)
      {
      	int ai,bi,ci;
      	scanf("%d%d%d",&ai,&bi,&ci);
      	if(a[ai-1][bi-1]>ci)
      	   {
			 a[ai-1][bi-1]=ci;
			 a[bi-1][ai-1]=ci;
      	   }
      }
      ans=0;
      if(n!=1)
         prim(0);
      cout<<ans<<endl;
   }
   return 0;
}