Java Solution for https://leetcode.com/problems/palindrome-number/

Understanding Problem

As per the problem we have been given an integer and we need to check if it is palindromic or not.

input_x    = 121
reversed_x = 121
input_x and reversed_x are palindromic
input_x    = -121
reversed_x = 121-
input_x and reversed_x are not palindromic

My Thought About Solution

• The solution looks pretty easy for me, we just have to read input integer digits backward and construct reversed integers.
• Then we can compare the input integer and reversed integer and return the result.
• One additional optimization we can do is that we can return negative integers without even checking if its palindromic or not since negative signs will make them not palindromic.
• Data structure: We are not using any collection, just integer is enough to hold the data.
  Time-complexity: O(length(N)) where N is the input integer
  Space-complexity: O(1) constant space

Pseudocode

1: First check if input integer is negative , if yes the return false , since input integers cannon be palindromic due do - sign
2: Construct reversed input integer by reading from last digit and append to reversed integer
3: Now compare the input integers and return the result

Solutions

Result

Our Code Runtime beats 99.96% of the submission. Nice job!

Conclusion

This Leetcode is a good problem to understand

• How to iterate over each digit in integer and play around with it.
• Optimizing solution by finding out cases where we don’t need to perform our core business logic.

Let me know if you have some opinion on the solution in the comment!

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Happy Leetcoding!