POJ2421

最小生成树，将Q行新建的桥转化为地图中i,j之间距离为0即可。代码如下： 

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int inf=0x3f3f3f3f;
const int maxn=105;
int mapp[maxn][maxn];
int vis[maxn];
int dis[maxn];
int n,m;
long long ans;
int a,b;
void init()
{memset(mapp,inf,sizeof(inf));memset(vis,0,sizeof(vis));ans=0;
}
void prime()
{for(int i=1;i<=n;i++)dis[i]=mapp[1][i];dis[1]=0;vis[1]=1;for(int v=0;v<n-1;v++){int minx=inf;int p=-1;for(int i=1;i<=n;i++)if(!vis[i]&&dis[i]<minx){p=i;minx=dis[i];}vis[p]=1;ans+=dis[p];for(int i=1;i<=n;i++)if(!vis[i]&&dis[i]>mapp[p][i])dis[i]=mapp[p][i];}
}
int main()
{scanf("%d",&n);for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)scanf("%d",&mapp[i][j]);scanf("%d",&m);for(int i=0;i<m;i++){scanf("%d%d",&a,&b);mapp[a][b]=mapp[b][a]=0;}prime();printf("%I64d\n",ans);return 0;
}