C语言通过递归调用函数解决求阶乘和ACKERMAN函数问题

输入整型n（n>=0），输出n!

#include<stdio.h>int fac(int n){    int sum;    if(n==1||n==0) sum=1;    else sum=n*fac(n-1);    return sum;}int main(){    int n;    scanf("%d",&n);    printf("%d",fac(n)); } 

#include<stdio.h>int fun(int a,int b){    int result;    if(a==0) result=b+1;    else if(b==0) result=fun(a-1,1);    else result=fun(a-1,fun(a,b-1));    return result;}int main(){    int a,b;    scanf("%d%d",&a,&b);    printf("%d\n",fun(a,b));}