LeetCode 7 Reverse Integer

*
* Reverse digits of an integer.
*
* Example1: x = 123, return 321
* Example2: x = -123, return -321
*
*first ,we should think the number over/underflow,it is very importent;
*then ,we need not to think the number is a negtive,like -123,it do not like string to integer
*so we can easy to deal the problems,
************************************************************************/

//Author: yqtao
//Email : [email protected]
//Date :2016.7.5

#include<iostream>
#include <vector>
using namespace std;
int reverse(int x) {
    int y = 0;
    int n;
    while (x != 0) {
        n = x % 10;
        //Checking the over/underflow.
        //Actually, it should be y>(INT_MAX-n)/10, but n/10 is 0, so omit it.
        if (y > INT_MAX / 10 || y < INT_MIN / 10) {
            return 0;
        }
        y = y * 10 + n;
        x /= 10;
    }
    return y;
}
//Actually,we can using long long is a 64bit numbers ,it cant to over/underflow
//for example,it is so smart;
int reverse1(int x) {
    long long res = 0;
    while (x) {
        res = res * 10 + x % 10;
        x /= 10;
    }
    return (res<INT_MIN || res>INT_MAX) ? 0 : res;
}
//test
int main()
{
    int x1 =-123,x2 = 1534236469,x3 = 4,x4 = -12340;
    cout << reverse1(x1) << endl;
    cout << reverse1(x2) << endl;
    cout << reverse1(x3) << endl;
    cout << reverse1(x4) << endl;
}