计算二项式系数使用循环和递归实现

#include <stdio.h>
double recurBinom(int, int);
double iterBinom(int, int);
double recurFact(int n);

int main(){
   int n,m;
   printf("n:(>=0): ");
   scanf("%d", &n);
   while (n < 0) 
   { /*error loop */
     printf("n:(>=0): ");
     scanf("%d", &n);
   }
   printf("m:(>=0): ");
   scanf("%d", &m);
   while (m < 0) 
   { /*error loop */
     printf("m:(>=0): ");
     scanf("%d", &m);
   }
  printf("n: %d m: %d Recursive Binomial coefficient is %f.
", n, m, recurBinom(n,m));
  printf("n: %d m: %d Iterative Binomial coefficient is %f.
", n, m, iterBinom(n,m));

}

double iterBinom(int n, int m)
{/* defined as n!/(m! - (n-m)!)*/
   int i;
   double nFact, mFact, nMinusMFact;
   if (n == m) return 1;
   if ((n==0) || (n == 1)) nFact = 1;
    else  {
	   nFact = 1;
       for (i = n; i > 1; i--)
           nFact *= i;
   }
   if  ((m==0) || (m == 1))  mFact = 1;
   else {
	   mFact = 1;
       for (i = m; i > 1; i--)
           mFact *= i;
   }
 if ( ((n-m) == 0) || ((n-m) == 1))  nMinusMFact = 1;
 else  {
	nMinusMFact = 1;
	for (i = n-m; i > 1; i--)
		nMinusMFact *= i;
 }
 return nFact/(mFact*nMinusMFact);
}

double recurFact(int n)
{ /*recursive version */
  if ((n==0) || (n==1))  return 1.0;
  return n*recurFact(n-1);
}


double recurBinom(int n, int m)
{ /*recursive version */
  return recurFact(n)/(recurFact(m)*recurFact(n-m));
}