[LeetCode9] Palindrome Number

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

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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.

Analysis:

Each time get the first and last digit to compare.

java , only use one class variable.

public class Solution {
    int y;
	public boolean isPalindrome(int x) {
        if(x<0) return false;
		y = x;
		return check(x,y);
    }
	public boolean check(int x, int x1){
		if(x==0) return true;
		if(check(x/10, y)){
			if(x%10 == y%10){
				y/=10;
				return true;
			}else {
				return false;
			}
		}else {
			return false;
		}
	}
}

c++

bool isPalindrome(int x) {
        if(x<0) return false;
    if(x == 0) return true;
    int div = 1;
    while(x/div>=10){
        div *=10;
    }
    while(x>0){
        int r = x%10;
        int l = x/div;
        if(l!= r) return false;
        x = (x%div)/10;
        div/=100;
    }
    return true;
    }