计算几何专项：UVa 11646

周长公式为2*L+acos((L*L-W*W)/(L*L+W*W))*sqrt(L*L+W*W)。然后二分L或者W就行了。

#include <iostream>#include <fstream>#include <cstring>#include <cstdio>#include <cmath>using namespace std;const double pi=3.14159265;const double eps=1e-10;double a,b;int dcmp(double x){    if(fabs(x)<eps) return 0;    else return x<0?-1:1;}int main(){    freopen("in.txt","r",stdin);    int kase=1;    while(~scanf("%lf : %lf",&a,&b))    {        cout<<"Case "<<kase++<<": ";        double L=0.0,R=200.0;        while(dcmp(L-R)<0)        {            double M=(L+R)/2;            double W=b*M/a;            double tmp=2*M+acos((M*M-W*W)/(M*M+W*W))*sqrt(M*M+W*W);            if(dcmp(tmp-400)>0) R=M;            else L=M;        }        printf("%.10f %.10f\n",L,b*L/a);    }    return 0;}