在这个简短的递归示例中，数字是如何存储、调用和添加的? [英] How are the numbers stored, called, and added in this short recursion example?

问题描述

首先，这不是家庭作业.我正在练习

First off, it's not homework. I'm practicing examples from http://codingbat.com/java/Recursion-1. Every time I think I'm beginning to understand recursion, I run into a problem that makes me realize I have no idea, and the only thing tutors or internet explanations ever say is that "the function calls itself until the base case is met."

public int sumDigits(int n) {
   if(n < 10) {
      return n;
   } else return sumDigits(n/10) + n % 10;
}

If I pass 115 to this on my computer, the output is 7 (as it should), but I don't understand how the program comes to this conclusion. Here is how I see it:

115 is not less than 10, so return the program with 115/10 (which is 11). 11 is not less than 10, so return the program with 11/10 (which is 1). Add this to 115%10 (which is 5). So how does this program get 7???

It seems like no matter how many examples I look at, I cannot find a pattern in how this works.

解决方案

Here is how it happens explained with a diagram

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