langc_algo_factorial_recursion.c

#include <stdio.h>

// general recursion
int factorial(int n)
{
  if(n==0)
    return 1;
  else
    return n * factorial(n-1);   
}

//tail recursion 
int tailfactorial(int n, int pren)
{
  if(n==1){
    return pren; //sum 
  }else{
    return tailfactorial(n-1, n*pren);
  }
}

//n repeat 
void reatfactorial(int n, int *sum)
{
	int i=0 ;
	
	for(i=1; i <= n;i++)
		*sum = *sum * i; 
	
}

int main(void) {
	int ret,sum=1;
	
	reatfactorial(4,&sum);
	printf("sum0= %d\n",sum);
	
	ret = factorial(4);
	printf("sum1= %d\n",ret);

	ret = tailfactorial(4,1);
	printf("sum2= %d\n",ret);

	return 0;
}