Palindrome Number.md

Algorithm

Convert the int to a String, and check to see if the String is a palindrome.

Solution

class Solution {
    public boolean isPalindrome(int x) {
        if (x < 0) {
            return false;
        }
        String s = String.valueOf(x);
        for (int i = 0; i < s.length() / 2; i++) {
            if (s.charAt(i) != s.charAt(s.length() - 1 - i)) {
                return false;
            }
        }
        return true;
    }
}

Time/Space Complexity

Max size of an int in Java is a constant 32 bits, so our String length will not exceed 32.

• Time Complexity
  • O(1) if you consider that int in Java is a constant 32 bits, so our String length will not exceed 32.
  • O(log n) if you allow x to grow infinitely large. The length of the String grows logarithmically as fast compared to the growth of x
• Space Complexity: O(1)

Follow-up Problem: "Don't use a String"

The String solution above is the most efficient and straightforward way to solve this problem. Skip the follow-up.

Links

• github.com/RodneyShag