C语言：函数-递归

#include <stdio.h>

int fn(int num);

int main()
{
    int i, sum;
    for(i=1,sum=0;i<=100;i++)
    {
        sum+=i;
    }
    printf("sum=%d\r\n",sum);

    sum=fn(5);
    printf("sum=%d\r\n",sum);
    return 0;
}

int fn (int num)
{
    if(num==1)
    {
        return 1;

    }
    return num +fn(num -1);
}
/*
  fn(1) = 1
  fn(2) = 2 + fn(2 - 1) = 2 + fn(1) = 2 + 1 = 3
  fn(3) = 3 + fn(3 - 1) = 3 + fn(2) = 3 + 2 + 1 = 6
  fn(4) = 4 + fn(4 - 1) = 4 + fn(3) = 4 + 3 + 2 + 1 = 10

  fn(100) = 100 + fn(100 - 1) = 100 + fn(99) = 100 + 99 ...

  100 的 累加
  相当于 100 加上 99 的 累加

*/

来源：CSDN

作者：hahahafree

链接：https://blog.csdn.net/weixin_43731793/article/details/103547010