离开递归调用时如何打印

Question

如何在递归调用后打印到屏幕上。例如在执行下面的 ackermann 函数时。

acker(1,2);
public int acker(int m, int n){
    System.out.println("Entered acker");
    if(m == 0)
        return n + 1;
    if(n == 0)
        return acker(m-1,1);
    return acker(m-1, acker(m, n - 1));
}

当我进入acker方法时我可以打印，但是在该方法完成调用自身后我将如何打印。例如输出将是：

Entered acker
Entered acker 
Entered acker 
Entered acker
//Here it would say leaving because its not making another recursive call

Answer 1

重构以将 return 值分配给变量，打印您的消息，然后 return 值：

public int acker(int m, int n){
    System.out.println("Entered acker");
    int result;
    if(m == 0)
        result = n + 1;
    else if(n == 0)
        result = acker(m-1,1);
    else
        result = acker(m-1, acker(m, n - 1));
    System.out.println( "Returning " + result + " from acker");
    return result; 
}

离开递归调用时如何打印

how to print when you have left a recursive call

java

printing

recursion