find the safest road HDU - 1596

城市与城市之间有安全指数，指数越大越安全，0即两城市不连通，安全度等于路线的安全指数相乘。输入两城市间最大的安全度。题目输入先输入连接矩阵，再输入起点终点。
链接http://acm.hdu.edu.cn/showproblem.php?pid=1596
ac：#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
const int N=1010;
const double eps = 1e-4;
double d
, w

;
bool vis[2000];
int t,n;
double maxn;

void dij( int s )
{
memset(vis, 0, sizeof(vis) );
memset(d,0,sizeof(d));
d[s] = 1;
for ( int i = 1; i <= n; i++ )
{
int u = 0;
for ( int j = 1; j <= n; j++ )
{
if ( !vis[j] && d[j] > d[u] )
{
u = j;
}
}
vis[u] = true;
for ( int j = 1; j <= n; j++ )
{
if ( !vis[j] && w[u][j] > eps )
{
if ( d[u] * w[u][j] > d[j] )
{
d[j] = d[u] * w[u][j];
}
}
}
}
}
int main()
{
while(cin>>n)
{

memset(w,0,sizeof(w));
for(int i=1; i<=n; i++)
{
for(int j=1;j<=n;j++)
{
scanf("%lf",&w[i][j]);
}
}

cin>>t;
for(int i=1;i<=t;i++)
{
int s,e;
scanf("%d %d",&s,&e);
dij(s);
if(d[e]==0)
printf("What a pity!\n");
else
printf("%.3f\n",d[e]);
}
}
return 0;
}