HDU-2073 无限的路

     http://acm.hdu.edu.cn/showproblem.php?pid=2073

　　代码如下：

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

double d[10005], D[10005];

double sqrt_2 = sqrt( 2.0 );

double dis( int x, int y )
{ 
return D[x + y] + d[x + y] - y * sqrt_2; 
}

int main()
{
int N;
    scanf( "%d", &N );
for( int i = 1, k = 1, j = 1; i < 10005; ++i )
    {
        d[i] = sqrt( ( double ) k ) + d[i-1];
        D[i] = i * sqrt_2 + D[i-1];
          k += 4 * i;
     }
while( N-- )
    {
int x1, y1, x2, y2;
        scanf( "%d %d %d %d", &x1, &y1, &x2, &y2 );
        printf( "%.3lf\n", fabs( dis( x2, y2 ) - dis( x1, y1 ) ) );
    }
return 0;
}