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Palindrome Number

LeetCode source

Solution

Intuition

The challenge with this problem is that you're not allowed to use any string. You have to take the integer and come up with a solution that doesn't employ string or any of its methods. From the first glance, what was apparent is that we'll need a data structure to hold the individual integers for comparison.

Algorithm

Details of the the algorithm for the solution is as follows:

  1. If it's a single digit, then it's a Palindrome Number.
  2. Ignore any negative integers.
  3. For all other types of integers, pop each digit and store them in a vector in order.
  4. Compare the (n + i)th integer with (vector.size() - 1 - i)th integer.
  5. If this comparisos fails (i.e. comparison == false) return false.
  6. Else continue the comparisons until i reaches the middle of the vector. If no false was return before, it means all the comparisons were true and therefore, the integer is a palindrome.

Complexity Analysis

  • Time Complexity: O(log⁡(n))
  • Space Complexity: O(log⁡(n))

AC Result

Test case result: 11509 / 11509 test cases passed

Status Runtime Memory
Accepted 36 ms 11.7 MB