c++随机生成服从指数分布均值为n的代码

#include <iostream>
#include <cmath>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
using namespace std;
double cls_random(double lambda)
{
    double pV = 0.0;
    while(true)
    {
        pV = (double)rand()/(double)RAND_MAX;
        if (pV != 1)
        {
            break;
        }
    }
    pV = (-1.0/lambda)*log(1-pV);
    return pV;
}
int main()
{
    int num = 50;
    double arr[500];
    for(int i=0; i<100; i++)
    {
        for(int j = 0; j<5; j++)
        {
            arr[i*5+j] = cls_random(0.02);
            cout<<arr[i*5+j]<< ' ';
        }
        cout<<endl;
    }

    double tmp = 0 ;
    for(int i = 0; i<500; i++)
        tmp+=arr[i];
    cout<<"tmp = "<<tmp/500<<endl;
    system("Pause");

    return 0;
}