#include<stdio.h>
#include<math.h>
int main()
{
double n,m,x1,y1,x2,y2;
while(~scanf("%lf %lf %lf %lf",&x1,&y1,&x2,&y2))
{
n=pow((x1-x2),2);
m=pow((y1-y2),2);
printf("%.2lf\n",sqrt(m+n));
}
return 0;
}
原文：http://www.cnblogs.com/digulove/p/4682308.html