codeforces #120 div2 B. Surrounded

水题....关键是没看懂题意
链接http://codeforces.com/contest/190/problem/B
求两个圆相夹的圆的半径
而且两个圆相交的时候输入0
一共3个情况

代码：

#include <stdio.h>#include <math.h>int main(){    double x1,y1,z1,x2,y2,z2,sign;    while(scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&z1,&x2,&y2,&z2)==6)    {    double num=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));    if(z1>num+z2||z2>num+z1)    {        if(z1>num+z2)        sign=(z1-num-z2)/2.0;        if(z2>num+z1)        sign=(z2-num-z1)/2.0;    }    else if(z1>num||z2>num||z1+z2>num)    sign=0;    else    sign=fabs(num-z1-z2)/2.0;    printf("%.15f\n",sign);    }}