Palindrome Number (Java and Python)

Determine whether an integer is a palindrome. Do this without extra space.

click to show spoilers.

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

	/*
	Determine whether an integer is a palindrome. Do this without extra space.
	click to show spoilers.
	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.
	*/
	// without consider about overflow
	public boolean isPalindrome(int x) {
	if (x<0){
	return false;
	}
	int current=0;
	int y=x;
	while (y!=0){
	current=current*10+(y%10);
	y=y/10;
	}
	return current==x;
	}
	// considered overflow
	public class Solution {
	public boolean isPalindrome(int x){
	if (x<0){
	return false;
	}
	int divider=1;
	while (x/divider>=10){
	divider*=10;
	}
	while (x!=0){
	int right=x%10;
	int left=x/divider;
	if (right!=left){
	return false;
	}
	x%=divider;
	x/=10;
	divider/=100;
	}
	return true;
	}

view raw PalindromeNumber.java hosted with ❤ by GitHub

	"""
	Determine whether an integer is a palindrome. Do this without extra space.
	click to show spoilers.
	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.
	"""
	class Solution:
	# @return a boolean
	def isPalindrome(self, x):
	if x<0:
	return False
	divider=1
	while(x/divider>=10):
	divider*=10
	while(x!=0):
	left=x/divider
	right=x%10
	if left!=right:
	return False
	x%=divider
	x/=10
	divider/=100
	return True

view raw PalindromeNumber.py hosted with ❤ by GitHub