7. Reverse Integer

7. Reverse Integer

Easy

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Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Input: 123
Output: 321

Example 2:

Input: -123
Output: -321

Example 3:

Input: 120
Output: 21

Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

class Solution {
public:
    int reverse(int x) {
        int res = 0;
        while(x) {
            int tmp = res*10 + x%10;
            if(tmp/10 != res) return 0;     // trick!
            res = tmp;
            x /= 10;
        }
        return res;
    }
};


class Solution {
public:
    int reverse(int x) {
        int origX = x;
        long res = 0;
        while(x) {
            res = res*10 + x%10;
            if(res>INT_MAX || res<INT_MIN) return 0;     // use MACRO   
            x/=10;
        }
        return res;
    }
};