Codeforces Looksery Cup 2015 H Degenerate Matrix binary pay attention to floating point traps, codeforceslooksery

Codeforces Looksery Cup 2015 H Degenerate Matrix binary pay attention to floating point traps, codeforceslooksery

#include <cstdio>#include <cstring>#include <algorithm>#include <string>#include <cmath>#include <iostream>using namespace std;bool fun(double l1,double r1,double l2,double r2){return (l1 <= r2 && l1 >= l2) || (l2 >= l1 && l2 <= r1);}int main() {    double a,b,c,d;    cin >> a >> b >> c >> d;        double r = 1000000000.0;    double l = 0;        for(int i = 0;i < 1000;i++){    double m = l + (r - l) /2.0;    double a1 = (a-m)*(d-m);    double a2 = (a-m)*(d+m);    double a3 = (a+m)*(d-m);    double a4 = (a+m)*(d+m);    double l1 = min(min(a1,a2),min(a3,a4));    double r1 = max(max(a1,a2),max(a3,a4));    a1 = (c-m)*(b-m);    a2 = (c-m)*(b+m);    a3 = (c+m)*(b-m);    a4 = (c+m)*(b+m);    double l2 = min(min(a1,a2),min(a3,a4));    double r2 = max(max(a1,a2),max(a3,a4));if(fun(l1,r1,l2,r2)){        r = m;     }    else{        l = m;    }    }    printf("%.10f\n",l);    return 0;    }