Question

所以我试图打印出递归指数方法的实际过程，然后打印出最后的值，但是我的for循环有问题。例如，如果用户输入4到4的功率，它应该打印4到4,4到3,4到2等，然后打印出正确的4到4的功率值，但我继续得到0的值结束。

import java.util.Scanner; 

public class Recursion
{
  public static void main(String[] args)
  {
    Scanner input = new Scanner(System.in);

    System.out.println("Enter base: ");
    int baseNum = input.nextInt();

    System.out.println("Enter exponent: ");
    int expNum = input.nextInt();

    for(int i = 1; i <= baseNum; ++i)
    {

    System.out.printf("\n%d to the %d", baseNum, expNum--);

    }

    System.out.printf("\nValue is %d",power(baseNum, expNum));
  }



  public static int power(int base, int exponent)
  {
    if(base == 0)
      return 1;

    else
      return exponent * power(base - 1, exponent);
  }
}

Answer 1

您将基数与指数混淆了。功率方法应该像这样定义：

public static int power(int base, int exponent) {
    if(exponent == 0) {
        System.out.println(1); // for display
        return 1;
    }
    else {
        int rem = power(base, exponent-1);
        if (rem > 1) {
            System.out.println(rem); // for display
        }
        return base * rem;
    }
}

<强> USAGE

public static void main(String[] args) {
    System.out.println(power(4,2)); // prints 16
}

Answer 2

求幂的递归定义是

x^n = x * x^(n-1)

请注意，指数会减少，而不是基数。

Answer 3

Power = base to exponent。你做错了。正确的方式 -

public static int power(int base, int exponent) {
    if(exponent == 0)
        return 1;
    else
        return base * power(base, exponent-1);
}

使上面的代码显示中间结果：

import java.util.Scanner;

public class Recursion {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.println("Enter base: ");
        int baseNum = input.nextInt();

        System.out.println("Enter exponent: ");
        int expNum = input.nextInt();

        int pow = power(baseNum, expNum);

    }

public static int power(int base, int exponent) {

    int pow = 0;

    if (exponent == 0) {
        pow = 1;
        System.out.println(base + " raised to " + exponent + " is " + pow);
    } else {

        pow = base * power(base, exponent - 1);
        System.out.println(base + " raised to " + exponent + " is " + pow);
    }

    return pow;

}

Answer 4

您的代码存在两个问题

指数在实际使用之前发生变异 expNum -
您在 power（）

以下是您的代码的编辑版本

import java.util.Scanner;

public class Recursion
{

    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);

        System.out.println("Enter base: ");
        int baseNum = input.nextInt();

        System.out.println("Enter exponent: ");
        int expNum = input.nextInt();

        for (int i = 1; i <= expNum; ++i)
        {

            System.out.printf("\n%d to the %d", baseNum, i);

        }

        System.out.printf("\nValue is %d", power(baseNum, expNum));
    }

    public static int power(int base, int exponent)
    {
        if (exponent == 0)
        {
            return 1;
        }

        else
        {
            return base * power(base, exponent - 1);
        }
    }
}

使用带递归的for循环

4 个答案: