题目：随机数函数a，产生0的概率0.7,1的概率0.3。怎样用该随机函数生成一个随机函数b，使得b产生0和1的概率为0.5 

代码实现如下：

#include<iostream>

using namespace std;
int main() {
	int alpha = 0;
	int beta = 0;
	int total = 0;
	for (int t = 0; t<10000; t++)
	{
		int small = 0;
		int big = 0;
		for (int i = 0; i<10000; i++)
		{
			int val = rand() % 10;
			if (val<3) small++;
			else big++;
		}
		if (big<7000) alpha++;
		else if (big>7000) beta++;
		if (big != 7000) total++;
	}
	cout << (float)alpha / (float)total << ' ' << (float)beta / (float)total << ' ' << (float)alpha / (float)total - (float)beta / (float)total << endl;
	return 0;
}