In java and using math, check if a number is a palindrome.

Question

hivejin · Accepted Answer

boolean isPalindromNumber(int n) {
    if(n == null)
        return true;
    return n == reverseNumber(n);
}

long reverseNumber(int n) {
    long rev = 0;
    while(n != 0)
        rev = rev * 10 + n % 10;
        n /= 10;
    }
    return rev;
}

Sigiloso · Answer

The above doesn't actually work for all cases. For example try 2020. This will solve for all possibilities:

public static boolean isPalindromeNumber(int n) {
    	int rev = 0;
    	int orig = n;
	 while(n != 0) {
	        rev = rev * 10 + n % 10;
	        n /= 10;
	  }
    	
    	if(orig % 10 == 0) {
    		rev *= 10;
    	}
    	return (orig == rev);
    }

Sigiloso · Answer

How is 2020 a palindrome?

Sigiloso · Answer

The point is to use math, as explicitly said.

Sigiloso · Answer

Convert to string and then either (a) revers and compare or (b) using two counters compare characters from both ends until they are not equal or they meet.

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