概率算法求PI的近似值

tuantuan

[code:1]
#include <time.h>
#include <stdlib.h>
#include <math.h>
#include <stdio.h>
//产生0到1之间的随机数
inline long double randf();
//概率算法求积分
long double HiborMiss(long double (*f) (long double),
unsigned long n);
//要积分的函数
long double f(long double x);
////////////////////////////////////////////////////
       
inline long double randf()
{
return rand()/(long double)(RAND_MAX);
}

long double HiborMiss(long double (*f) (long double),
unsigned long n)
{
unsigned long k=0;
unsigned long i;
for(i=0;i<n;i++)
{
  long double x = randf();
  //printf("x=%f",(double)x);
  long double y = randf();
  //printf("y=%f",(double)y);
  if(!(y>(*f)(x))) k++;
}
printf("k=%lu\nn=%lu\n",k,n);
return 4*k/(long double)n;
}
long double f(long double x)
{
return (long double)(sqrtl(1-x*x));
}


int main(int argc, char *argv[])
{
  long double (*p) (long double);
  p=f;
  srand((unsigned)(time(NULL)/2));
  printf("%1.10f\n",(double)HiborMiss(p,100000000));
       //100000000为迭代次数。
  system("PAUSE");       
  return 0;
}
[/code:1]