#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#if RAND_MAX<(1u<<15)
#define getRandom (rand()+rand()/(RAND_MAX+1.0))/(RAND_MAX+1.0)
#else
#define getRandom rand()/(RAND_MAX+1.0)
#endif

void calSum(double *A,unsigned n)
{/*將比例轉為累進機率*/
	unsigned i;
	double sum;
	for(i=1;i<n;++i)
		A[i]+=A[i-1];
	sum=A[n-1];
	for(i=0;i<n;++i)
		A[i]/=sum;
}
unsigned getRandIdx(double *A,unsigned n)
{/*依據機率，亂數取得對應的index*/
	double x=getRandom;
	int l,r,m;
	if(A[0]>x)
		return 0;
	/*這邊用二分搜尋法*/
	for(l=0,r=n-1;r>l+1;)
	{
		m=(l+r)/2;
		if(A[m]>x)
			r=m;
		else
			l=m;
	}
	return r;
}
int main()
{
	int i,k;
	double bound[]={1.3,1.5,1.2,1.1,1.0,0.9};/*加權，多奇怪的比例都可以*/
	int count[]={0,0,0,0,0,0};
	unsigned n=sizeof(bound)/sizeof(*bound);
	srand(time(NULL));
	/*將比例關係轉為累進機率*/
	calSum(bound,n);
	/*輸出各點數機率(理論值)*/
	printf("probability in theorem:\n");
	for(i=0;i<n;++i)
		printf("%d\t%.2lf%%\n",i+1,(bound[i]-(i==0?0.0:bound[i-1]))*100);
	/*讓使用者輸入取樣次數*/
	printf("\ninput number of sample:");
	scanf(" %d",&k);
	/*取樣*/
	for(i=0;i<k;++i)
		++count[getRandIdx(bound,n)];
	/*輸出結果*/
	for(i=0;i<n;++i)
		printf("%d\t%.2lf%% (%d/%d)\n",i+1,(double)count[i]/k*100.0,count[i],k);
	return 0;
}