在同一个条件中使用 2 个递归语句如何工作？

Question

I'm trying to understand how this recursive code works, and I haven't found anything similar to it on the internet.

public void doSomething(int n)
{
    if (n > 0)
    {
        doSomething(n-1);
        System.out.println(n);
        doSomething(n-1);
    }
}

Why is the output 1213121?

Answer 1

It is quite simple.

You call doSomething(3) -> doSomething(2) -> doSomething(1) -> doSomething(0) -> condition is not met so you return -> println(1) -> doSomething(0) -> condition is not met so you return .

Now you are at the end of the function doSomething(1) . println(2) is called. And you call doSomething(1) same as before.

When you return from doSomething(2) , println(3) is called...