java - 斐波那契轨迹

Question

我只是想提前说明这是一项家庭作业。我已经尝试了很多不同的方法来解决这个问题，以至于我不知道为什么我没有得到想要的输出。

问题

编写一个程序来跟踪斐波那契数是如何递归生成的(对于任何 N)并以下列方式显示跟踪:

示例 (N=4):

Entering level 0
Entering level 2
Entering level 4
Exiting level 4
Entering level 3
Exiting level 3
Exiting level 2
Entering level 1
Entering level 3
Exiting level 3
Entering level 2
Entering level 4
Exiting level 4
Entering level 3
Exiting level 3
Exiting level 2
Exiting level 1
Exiting level 0

---

我的主要:

public class A5main {

public static void main(String[] args) {
    //n holds user input
    //level is the current level of the tree
    //fibonacci is a5class object
    int n;
    int level=0;
    a5class fibonacci= new a5class();
    Scanner keyboard = new Scanner(System.in);

    //Ask user for input

   System.out.println("Enter a number up to which Fibonacci series to print: ");
   n = keyboard.nextInt();
   System.out.println("Fibonacci trace of: " + n);

    //Pass input to fibonacci.trace method with arguments n, level.
   fibonacci.trace(n,level);

}
}

我的类(class):

 package a5main;
 public class a5class {
    int fibWork;
   public a5class()     
{ 
}
public int trace(int t, int level)
{
    //Accepts t and level as an argument.
    //Lets uer know what level they are entering 
    System.out.println("Now entering level " + level);
    //If t<=1 just return the value
        if (t<=1)
        {
            System.out.println ("\tNow exiting level " + level);
            return t;

        }
        //Else use recurssion to figure out the fibonacci sequence
        //and determine what level you are on.
        else
        {
            fibWork = trace(t-1, level+1) + trace(t-2, level+1);
            System.out.println ("\tNow exiting level " + level);
            return t; 
        }
}
}

(我把\t 放在那里所以我现在可以更容易地看到它退出的位置)

我的输出:

Enter a number up to which Fibonacci series to print: 
4
Fibonacci trace of: 4
Now entering level 0
Now entering level 1
Now entering level 2
Now entering level 3
     Now exiting level 3
Now entering level 3
     Now exiting level 3
     Now exiting level 2
Now entering level 2
     Now exiting level 2
     Now exiting level 1
Now entering level 1
Now entering level 2
     Now exiting level 2
Now entering level 2
     Now exiting level 2
     Now exiting level 1
     Now exiting level 0

我还尝试过不将 'level 传递给方法，并在创建对象时在我的公共(public) a5class 中将其设置为 0，但到目前为止还没有成功。

虽然我的可能离得不远，但我注意到它退出了第 3 级，然后在下一个序列中重新进入，这在逻辑上似乎也不正确。

我感谢任何帮助或指导。即使只是指向正确方向的指针也会受到赞赏。我认真对待我的编程并想真正理解它。我不想“假装”通过它并获得一文不值的学位。

谢谢!

Answer 1

从预期的输出中，您会看到程序希望直接从 0 级进入 2 级，并从 2 级进入 4 级。只有在第一次递归调用中将 2 添加到该级别时才会发生这种情况:

fibWork = trace(t-2, level+2) + trace(t-1, level+1);