具有两个输入的递归 function

Question

Write a recursive function called print_num_pattern() to output the following number pattern.

Given a positive integer as input (Ex: 12), subtract another positive integer (Ex: 3) continually until 0 or a negative value is reached, and then continually add the second integer until the first integer is again reached.

Ex. If the input is:

12 3

the output is:

12 9 6 3 0 3 6 9 12

Here's what I tried:

num1 = 12

num2 = 3


def print_num_pattern(num1,num2): 

    if (num1 == 0 or num1 < 0): 
        print(num1, end = ' ') 
        return

    print(num1, end = ' ') 
    print_num_pattern(num1 - num2) 

    print(num1, end = ' ') 

print_num_pattern(num1,num2)

Answer 1

The most obvious error is that you're calling print_num_pattern(num1 - num2) with only one out of two parameters

def print_num_pattern(num1,num2): 

    if (num1 == 0 or num1 < 0): 
        print(num1, end = ' ') 
        return

    print(num1, end = ' ') 
    print_num_pattern(num1 - num2, num2) 

    print(num1, end = ' ')

It works fine after that

>>> print_num_pattern(12, 3)
12 9 6 3 0 3 6 9 12 

Answer 2

You are missing an argument in your recursive call. You need to replace this:

print_num_pattern(num1 - num2) 

with this:

print_num_pattern(num1 - num2, num2)

Answer 3

import java.util.Scanner;

public class NumberPattern {

   // TODO: Write recursive printNumPattern() method

  static void printNumPattern(int num1, int num2){

     if(num1 == -1 || num1 < 0)
     {
      System.out.print(num1 + " ");

      return;
     }
 System.out.print(num1 + " ");

           printNumPattern(num1 - num2, num2);

           System.out.print(num1 + " " );
  }
  
   public static void main(String[] args) { 

      Scanner scnr = new Scanner(System.in);

      int num1;

      int num2;
      
      num1 = scnr.nextInt();

      num2 = scnr.nextInt();

      printNumPattern(num1, num2); 
   } 
}