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Find the Sum of Digits in a Number

Certification: Basic Level Accuracy: 51.19% Submissions: 631 Points: 5

Write a Python program that calculates the sum of all digits in a given integer.

Example 1
    
  
  • Input: 12345
    • 
  
  • Output: 15
    • 
  
  • Explanation: 
    
      
      
    • Step 1: Take the digit 5 (12345 % 10 = 5). Sum = 5.
      • 
      
    • Step 2: Remove the last digit (12345 // 10 = 1234).
      • 
      
    • Step 3: Take the digit 4 (1234 % 10 = 4). Sum = 5 + 4 = 9.
      • 
      
    • Step 4: Remove the last digit (1234 // 10 = 123).
      • 
      
    • Step 5: Take the digit 3 (123 % 10 = 3). Sum = 9 + 3 = 12.
      • 
      
    • Step 6: Remove the last digit (123 // 10 = 12).
      • 
      
    • Step 7: Take the digit 2 (12 % 10 = 2). Sum = 12 + 2 = 14.
      • 
      
    • Step 8: Remove the last digit (12 // 10 = 1).
      • 
      
    • Step 9: Take the digit 1 (1 % 10 = 1). Sum = 14 + 1 = 15.
      • 
      
    • Step 10: No more digits left, return the sum 15.
      • 
    
    
  
    •
Example 2
    
  
  • Input: -678
    • 
  
  • Output: 21
    • 
  
  • Explanation: 
    
      
      
    • Step 1: Convert to positive number. -678 becomes 678.
      • 
      
    • Step 2: Take the digit 8 (678 % 10 = 8). Sum = 8.
      • 
      
    • Step 3: Remove the last digit (678 // 10 = 67).
      • 
      
    • Step 4: Take the digit 7 (67 % 10 = 7). Sum = 8 + 7 = 15.
      • 
      
    • Step 5: Remove the last digit (67 // 10 = 6).
      • 
      
    • Step 6: Take the digit 6 (6 % 10 = 6). Sum = 15 + 6 = 21.
      • 
      
    • Step 7: No more digits left, return the sum 21.
      • 
    
    
  
    •
Constraints
    
  
  • -10^9 ≤ number ≤ 10^9
    • 
  
  • For negative numbers, ignore the negative sign
    • 
  
  • Time Complexity: O(log n), where n is the input number
    • 
  
  • Space Complexity: O(1)
    •
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Hint
Solution

Solution Hints

    
  
  • Convert to string and iterate: sum(int(digit) for digit in str(abs(number)))
    • 
  
  • Use modulo and division: while number > 0: sum += number % 10; number //= 10
    • 
  
  • Use recursion: def sum_digits(n): return 0 if n == 0 else abs(n) % 10 + sum_digits(abs(n) // 10)
    • 
  
  • Use map(): sum(map(int, str(abs(number))))
    •

The following are the steps to find the sum of digits in a number:

  • Create a function sum_of_digits that takes a number n as input.

  • Handle the case of negative numbers by converting to positive (using abs(n)).

  • Initialize a variable digit_sum to 0 to store the running sum.

  • Extract each digit from the number using a loop:
   
    • Use the modulo operator (%) to get the last digit: digit = n % 10
   
    • Add this digit to the running sum: digit_sum += digit
   
    • Remove the last digit from the number using integer division: n //= 10
   
    • Continue this process until no digits remain (n becomes 0)
   
    

  • Return the final sum.

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