C++ Solution, keep two divs, one for get first digit, one for the last.

  • 4
    class Solution {
        bool isPalindrome(int x) {
            if(x<0) return false;
            int div2 = 1;
            while(x/div2 >= 10)
            int div1 = 1;
            while(div1 < div2)
                if((x/div1)%10 != (x/div2)%10) return false;
                div1 *= 10;
                div2 /= 10;
            return true;

  • 3

    What's the real meaning of using extra space. Does using div1 and div2 mean use extra space?

  • 0

    div1 and div2 is constant space, so doesn't count for extra space. In algorithm realm, extra space means space that proportional to the problem itself.

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