algoadvance

Given an integer num, return whether the value of num after performing a double reversal is the same as num.

  1. Reverse the digits of num.
  2. Reverse the digits of the resulting number.

Essentially, you need to determine if the number remains the same after this double reversal. For example:

Clarifying Questions

  1. Can the number be negative?
    • No, according to the problem description, num will be a non-negative integer.
  2. Is there a size limit for the number?
    • The number will be within the constraints typical for a standard integer in programming problems unless otherwise specified.

Strategy

The double reversal of any number that does not end in 0 (except for 0 itself) will result in the same number. Therefore, we can conclude that a non-zero number which ends in 0 will not remain the same, while others will.

Cases

  1. If num == 0, return True.
  2. If num % 10 == 0 and num != 0, return False.
  3. Otherwise, return True.

Time Complexity

The time complexity of this solution is (O(1)) because the checks are simple arithmetic operations and do not depend on the size of the input.

Python Code

def isSameAfterReversals(num: int) -> bool:
    if num == 0:
        return True
    if num % 10 == 0:
        return False
    return True

Explanation

  1. Case num == 0:
    • If the number is zero, reversing it any number of times will still yield zero.
  2. Case num % 10 == 0 and num != 0:
    • If the number ends in zero but is not zero, reversing it will lead to a loss of trailing zeros which cannot be recovered by further reversals.
  3. Otherwise:
    • Any other number will remain the same after a double reversal because the process of reversing does not fundamentally change the digits except for removing leading zeros (which aren’t present in this case).

This method ensures an efficient and clear check for the condition mentioned in the problem statement.

Try our interview co-pilot at AlgoAdvance.com