HDU 3405 World Islands（最短路）

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最短路变形。。

#include "stack"#include "cstdio"#include "iostream"#include "cmath"#include "set"#include "sstream"#include "cctype"#include "string"#include "cstring"#include "algorithm"#include "queue"using namespace std;#define LL long long#define inf 0x7ffffff#define pa pair<int,int>#define pi 3.1415926535897932384626433832795028841971const int M=1005;double map[M][M],vis[1100],dis[1100];int ant,n,m;double a[1000],b[1000],c,d;double prim(int t){    int i,j,k;    memset(vis,0,sizeof(vis));    vis[t]=1;    for(i=0;i<n;i++)    {       dis[i]=map[i][0];    }    vis[0]=1;    if(t==0)    {       for(i=0;i<n;i++)       {             dis[i]=map[i][1];       }       vis[1]=1;    }    double s=0;    for(j=1;j<n-1;j++)    {                double minn=inf;        for(i=0;i<n;i++)        {            if(!vis[i]&&minn>dis[i])            {                minn=dis[i];                k=i;            }        }        vis[k]=1;        s+=minn;        for(i=0;i<n;i++)        {            if(!vis[i]&&dis[i]>map[k][i])            dis[i]=map[k][i];        }              }    return s;}int main(){    int i,j;    int t;    cin>>t;    while(t--)    {    cin>>n;    for(i=0;i<n;i++)    {        cin>>a[i]>>b[i];        map[i][i]=0;        for(j=0;j<=i;j++)        {            map[i][j]=map[j][i]=sqrt((a[i]-a[j])*(a[i]-a[j])+(b[i]-b[j])*(b[i]-b[j]));        }    }    d=inf;    for(i=0;i<n;i++)    {          c=prim(i);          d=min(c,d);    }    printf("%.2lf\n",d);        }    }

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