Easy Coding Problem: Palindrome Number

Nitin Kumar

2 min read

·

Sep 18, 2026

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The problem is to check whether a number is a palindrome and provide binary output accordingly. A palindrome is a string that is read the same from left to right and right to left.

This problem can be solved in two ways: first, convert the integer to a string and compare it with its reverse. The second way is to reverse the number by dividing it by 10 in a loop and storing the number in a temp variable.

Example:

• Input: 121
• Answer: True/1

String Comparison

Python has asimple way of reversing the number by using [::-1]. This is different from[:-1], as this will read the string from the first to second last characters. [::-1] uses empty start, empty stop, step -1 while [:-1] uses empty start, stop -1, step 1.

class palindromeNumber:
 # Time complexity: O(log10(x)); Space complexity: O(log10(x))
 def isPalindromeString(self, x: int) -> bool:
  # Convert the number to a string.
  number = str(x)
  # Compare the string with its reversed version.
  return number == number[::-1]

 
# Run the following code only when this file is executed directly.
if __name__ == "__main__":
 # Read a number from the user.
 x = int(input("Enter a number: "))

 # Display the result from the string method.
 print(palindromeNumber().isPalindromeString(x))

Integer Comparision

Python has a inbuild modulas operater which is %. So 10/3 will give you 3.333… as the result. But 10 % 3 will give you 1 as a remainder.

Apart from modulus, Python also has a floor division operator, which will give the quotient of the equation and is written as two slashes, like //. So 10//3 will give only 3. Kindly note that this operator only provides an integer result.

class palindromeNumber:
 # Time complexity: O(log10(x)); Space complexity: O(1)
 def isPalindromeInt(self, x: int) -> bool:
  # Reject negative numbers.
  if x < 0:
   # A negative number is not a palindrome.
   return False
  # Handle zero as a special case.
  if x == 0:
   # Zero is a palindrome.
   return True
  # Save the original number for comparison.
  original = x
  # Start with an empty reversed number.
  reversed_number = 0
  # Continue while digits remain in x.
  while x:
   # Remove and retrieve the last digit.
   digit = x % 10
   x //= 10
   # Append the digit to the reversed number.
   reversed_number = reversed_number * 10 + digit

  # Return whether the number equals its reverse.
  return original == reversed_number
 

# Run the following code only when this file is executed directly.
if __name__ == "__main__":
 # Read a number from the user.
 x = int(input("Enter a number: "))
 # Display the result from the integer method.
 print(palindromeNumber().isPalindromeInt(x))
 # Display the result from the string method.
 print(palindromeNumber().isPalindromeString(x))
 # Display the result from the half-integer method.
 print(palindromeNumber().isPalindromeHalfInt(x))