遞迴

1. 函式呼叫自己本身如：

   void recursion() {
      recursion();
   }
   
   int main(){
      recursion();
   }
   

2. 遞迴必須謹慎使用，最常舉的遞迴例子為階層運算：

   [dywang@deyu zzz]$ vim function8.c
   [dywang@deyu zzz]$ cat function8.c
   #include <stdio.h>
   
   int factorial(unsigned int i) {
      if(i <= 1) return 1;
   
      return i * factorial(i-1);
   }
   int  main() {
   	int i = 15;
   	printf("Factorial of %d is %d\n", i, factorial(i));
   	return 0;
   }
   

3. 編譯成功

   [dywang@deyu zzz]$ gcc -o function8 function8.c
   

4. 執行結果

   [dywang@deyu zzz]$ ./function8
   Factorial of 15 is 2004310016