void recursion()

{

   statements;

   ... ... ...

   recursion(); /* 函数调用自身 */

   ... ... ...

}

int main()

{

   recursion();

}

#include <stdio.h>

double factorial(unsigned int i)

{

   if(i <= )

   {

      return ;

   }

   return i * factorial(i - );

}

int  main()

{

    int i = ;

    printf("%d 的阶乘为 %f\n", i, factorial(i));

    return ;

}

#include <stdio.h>

int fibonaci(int i)

{

   if(i == )

   {

      return ;

   }

   if(i == )

   {

      return ;

   }

   return fibonaci(i-) + fibonaci(i-);

}

int  main()

{

    int i;

    for (i = ; i < ; i++)

    {

       printf("%d\t\n", fibonaci(i));

    }

    return ;

}

#include <stdio.h>

#include <stdarg.h>

double average(int num,...)

{

    va_list valist;

    double sum = 0.0;

    int i;

    /* 为 num 个参数初始化 valist */

    va_start(valist, num);

    /* 访问所有赋给 valist 的参数 */

    for (i = ; i < num; i++)

    {

       sum += va_arg(valist, int);

    }

    /* 清理为 valist 保留的内存 */

    va_end(valist);

    return sum/num;

}

int main()

{

   printf("Average of 2, 3, 4, 5 = %f\n", average(, ,,,));

   printf("Average of 5, 10, 15 = %f\n", average(, ,,));

}