阿里编程题

题目：小明向他的女朋友仙仙求婚，在求婚戒指上刻了一个大大的爱心。仙仙看到爱心想考验一下小明，出了一道题。方程(x2+y2−1)2−x2y2=0，这个点在这个爱心里面的概率是多少，精确到0.1（小数点后保留一位小数，比如0.1, 0.2等）

#include <iostream>#include <math.h>using namespace std;/*生成标准正态分布随机数*/double gaussRand(){    static double V1,V2,S;    static int  phase=0;    double X;    if(phase==0){        do{            double U1=(double)rand()/RAND_MAX;            double U2=(double)rand()/RAND_MAX;            V1=2*U1-1;            V2=2*U2-1;            S=V1*V1+V2*V2;        }while(S>=1||S==0);        X=V1*sqrt(-2*log(S)/S);    }    else        X=V2*sqrt(-2*log(S)/S);    phase=1-phase;    return X;}/*将随机值从正态分布N(0,1)转化到高斯分布N(mu,sigma)*/double gaussValue(double val,double mu,double sigma){    return mu+sigma*val;}/*判断随机值是否在曲线内*/bool isInside(double x,double y){       double x2=x*x;    double y2=y*y;    double temp=x2+y2-1;    return (temp*temp-x2*y2)>0?false:true;}/*模拟*/double learnCurve(double mu1,double sigma1,double mu2,double sigma2){    int n=10000;//模拟次数    int count=0;    int i=n;    while(i-->0){        double x=gaussValue(gaussRand(),mu1,sigma1);        double y=gaussValue(gaussRand(),mu2,sigma2);        if(isInside(x,y))            count++;    }    return (double) count/n;}int main(){    double mu1,mu2,sigma1,sigma2;    cin>>mu1>>sigma1>>mu2>>sigma2;    double res=learnCurve(mu1,sigma1,mu2,sigma2);    printf("%.1f\n",res);    return 0;}
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参考：

http://blog.csdn.net/shijing_0214/article/details/60465542
http://www.cnblogs.com/tsingke/p/6194737.html

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