9. 回文数

9. 回文数

class Solution {
public:
    bool isPalindrome(int x) {
        if(x < 0)
            return false;
        int num = 0;
        int d = x;
        while(x)
        {
            if(num >= INT_MAX / 10)
                return false;
            num = num * 10 + x % 10;
            x /= 10;
        }
        return num == d;
    }
};

T(n) : O(logn)

每次迭代除以10，所以是logn

题解

class Solution {
public:
    bool isPalindrome(int x) {
        if(x < 0  || x % 10 == 0 && x != 0)
            return false;
        int num = 0;
        while(x > num)
        {
            num = num * 10 + x % 10;
            x /= 10;
        }
        return num == x || num / 10 == x;;
    }
};