Palindrome Number Problem LeetCode (Check if a number is a palindrome)

Given an integer x, return true if x is palindrome integer.

An integer is a palindrome when it reads the same backward as forward. For example, 121 is palindrome while 123 is not.

 Example 1:

Input: x = 121
Output: true

Example 2:

Input: x = -121
Output: false
Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.

Example 3:

Input: x = 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

Example 4:

Input: x = -101
Output: false

 NOTE:

• -231 <= x <= 231 - 1

 Follow up: Could you solve it without converting the integer to a string?

This problem is popular in LeetCode, GeeksForGeeks, and many other forums - Ref 1, Ref 2 A collection of hundreds of interview questions and solutions are available in our blog at Interview Question Solutions

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SOLUTION:
Source code: Java

	import java.text.DateFormat;
	import java.text.SimpleDateFormat;
	import java.util.ArrayList;
	import java.util.Date;
	import java.util.HashMap;
	import java.util.List;
	import java.util.Map;
	/**
	* Determine whether an integer is a palindrome. Do this without extra space.
	*
	* Some hints: Could negative integers be palindromes? (ie, -1)
	*
	* If you are thinking of converting the integer to string, note the restriction
	* of using extra space.
	*
	* You could also try reversing an integer. However, if you have solved the
	* problem "Reverse Integer", you know that the reversed integer might overflow.
	* How would you handle such case?
	*
	* There is a more generic way of solving this problem. TODOS:
	* Handle overflow
	*/
	/**
	*
	* @author rbaral
	*
	*/
	public class PalindromeNumber {
	public static void main(String[] args) {
	boolean testEnabled = false;
	if (testEnabled) {
	performTest();
	} else {
	DateFormat format = new SimpleDateFormat("YYYY-M-d:H:m:s:S");
	System.out.println(format.format(new Date()));
	int num = 191;
	System.out.println("output is:" + isPalindrome(num));
	System.out.println(format.format(new Date()));
	}
	}
	public static boolean isPalindrome(int x) {
	if (x < 0)//negative numbers are not palindrome
	{
	return false;
	}
	if (x < 10)//one digit is always a palindrome
	{
	return true;
	}
	//find the reverse of the number and check if the reverse is equal to it
	int rev = 0;
	int temp = x;
	while (temp > 0) {
	rev = temp % 10 + rev * 10;
	temp /= 10;
	}
	System.out.println("reverse is:" + rev + " number is:" + x);
	if (rev == x) {
	return true;
	}
	return false;
	}
	public static void performTest() {
	Map<Integer, Boolean> testCases = new HashMap<Integer, Boolean>();
	List<String> failedCases = new ArrayList<String>();
	boolean result = false;
	testCases.put(121, true);
	testCases.put(122, false);
	testCases.put(-2147483648, false);
	testCases.put(11, true);
	for (int testCase : testCases.keySet()) {
	result = isPalindrome(testCase);
	if (result != testCases.get(testCase)) {
	failedCases.add("Failed for:{" + testCase + "} got:" + result + " expected:" + testCases.get(testCase));
	}
	}
	System.out.println("TEST RESULT, Passed:" + (testCases.size() - failedCases.size()) + " failed:" + failedCases.size());
	for (String failure : failedCases) {
	System.err.println(failure);
	}
	}
	}

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