009.Palindrome Number

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Solution 1: accepted

The given number has to be an integer. So “if (reversed > 214748364 || reversed < -214748364)” would be fine.
Even if it is a fit, the is not a palindrome. 

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public class Solution {
    public boolean isPalindrome(int x) {
       if (x < 0 || x >= 2147483642) // making huge difference in performance, probably due to the speciality of the test cases 
		return false;
	int original = x;
	int reversed = 0;
	int digit = 0;
	while (x != 0) {
		if (digit == 9) {
			if (reversed > 214748364 || reversed < -214748364)
				return false;
		}
	
		reversed = reversed * 10 + x % 10;
		x = x / 10;
		digit++;
	}
	return original == reversed;
    }
}

Solution 2: accepted 261ms

Simplified. But do we need to check the entire number?

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public boolean isPalindrome(int x) {
    if (x < 0 || x > 0 && x % 10 == 0)
        return false;
    int original = x;
    int reverse = 0;
    while (x != 0) {
        reverse = reverse * 10 + x % 10;
        x /= 10;
    }
    return reverse == original;
}
Improvement: accepted 221ms

We only need to check half of the number

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public boolean isPalindrome(int x) {
    if (x < 0 || x > 0 && x % 10 == 0)
        return false;
    int reverse = 0;
    while (x > reverse) {
        reverse = reverse * 10 + x % 10;
        x /= 10;
    }
    return (x == reverse || x == reverse/10);  // for 123321 and 12321
}