9. Palindrome Number

description:

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

Example 1:

Input: 121
Output: true
Example 2:

Input: -121
Output: false
Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
Example 3:

Input: 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

my answer:

感恩

class Solution {
public:
    bool isPalindrome(int x) {
        if(x<0) return false;
        string s;
        while(x!=0){
            int add = x%10;
            s+='0'+add;
            x = x/10;
        }
        int n = s.size();
        for(int i = 0; i < n/2; i++){
            if(s[i]!=s[n-1-i]) return false;
        }
        return true;
    }
};

大佬的answer：

class Solution {
public:
    bool isPalindrome(int x) {
        if(x<0||(x%10==0&&x!=0))return false;
        return reverse(x)==x;
    }
    int reverse(int x){
        int res = 0;
        while(x!=0){
            if(res>INT_MAX/10)return -1;//这里很有意思，溢出好像都是判断INT_MAX/10的？
            res = res*10 + x%10;
            x /= 10;
        }
        return res;
    }
};

relative point get√：

emmm, string and integer 交换好像都需要'0' 作为跳板咩...？

hint :

res>INT_MAX/10)return -1
res = res*10 + x%10;
x /= 10;