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Sum of Digits of a Given Number Recursively

Certification: Intermediate Level Accuracy: 75% Submissions: 4 Points: 5

Write a Python function to compute the sum of digits of a given integer using recursion.

Example 1
    
  
  • Input: num = 123
    • 
  
  • Output: 6
    • 
  
  • Explanation: 
      
    
    • Step 1: Apply recursive function to 123.
      
        
        
      • Get the last digit: 123 % 10 = 3
        • 
        
      • Remove the last digit: 123 // 10 = 12
        • 
        
      • Recursively calculate the sum of digits of 12
        • 
      
      
    
      • 
    
    • Step 2: Apply recursive function to 12.
      
        
        
      • Get the last digit: 12 % 10 = 2
        • 
        
      • Remove the last digit: 12 // 10 = 1
        • 
        
      • Recursively calculate the sum of digits of 1
        • 
      
      
    
      • 
    
    • Step 3: Apply recursive function to 1.
      
        
        
      • Get the last digit: 1 % 10 = 1
        • 
        
      • Remove the last digit: 1 // 10 = 0
        • 
        
      • Since we've reached 0, return 1
        • 
      
      
    
      • 
    
    • Step 4: Combine the results: 3 + (2 + 1) = 3 + 3 = 6.
      • 
    
    • Step 5: Return 6 as the sum of digits.
      • 
  
    •
Example 2
    
  
  • Input: num = 9875
    • 
  
  • Output: 29
    • 
  
  • Explanation: 
      
    
    • Step 1: Apply recursive function to 9875.
      
        
        
      • Get the last digit: 9875 % 10 = 5
        • 
        
      • Remove the last digit: 9875 // 10 = 987
        • 
        
      • Recursively calculate the sum of digits of 987
        • 
      
      
    
      • 
    
    • Step 2: Apply recursive function to 987.
      
        
        
      • Get the last digit: 987 % 10 = 7
        • 
        
      • Remove the last digit: 987 // 10 = 98
        • 
        
      • Recursively calculate the sum of digits of 98
        • 
      
      
    
      • 
    
    • Step 3: Apply recursive function to 98.
      
        
        
      • Get the last digit: 98 % 10 = 8
        • 
        
      • Remove the last digit: 98 // 10 = 9
        • 
        
      • Recursively calculate the sum of digits of 9
        • 
      
      
    
      • 
    
    • Step 4: Apply recursive function to 9.
      
        
        
      • Get the last digit: 9 % 10 = 9
        • 
        
      • Remove the last digit: 9 // 10 = 0
        • 
        
      • Since we've reached 0, return 9
        • 
      
      
    
      • 
    
    • Step 5: Combine the results: 5 + (7 + (8 + 9)) = 5 + (7 + 17) = 5 + 24 = 29.
      • 
    
    • Step 6: Return 29 as the sum of digits.
      • 
  
    •
Constraints
    
  
  • 0 <= number <= 10^9
    • 
  
  • Time Complexity: O(log n) where n is the number
    • 
  
  • Space Complexity: O(log n) due to recursion stack
    •
NumberRecursionWiproIBM
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Hint
Solution

Solution Hints

    
  
  • Use modulo and integer division to extract digits: number % 10 and number // 10
    • 
  
  • Base case: if the number is 0, return 0.
    • 
  
  • Recursive case: return the last digit plus the sum of the remaining digits.
    •

Steps to solve by this approach:

 Step 1: Define the base case: if number is 0, return 0

 Step 2: Extract the rightmost digit using modulo operation (number % 10)

 Step 3: Remove the rightmost digit using integer division (number // 10)

 Step 4: Recursively call the function with the remaining digits

 Step 5: Add the current digit to the sum returned by recursive call

 Step 6: Continue recursion until all digits are processed

 Step 7: Return the total sum of all digits in the number

Submitted Code :