acm/leetcode/7.reverse-integer.cpp

/*
 * @lc app=leetcode id=7 lang=cpp
 *
 * [7] Reverse Integer
 *
 * https://leetcode.com/problems/reverse-integer/description/
 *
 * algorithms
 * Easy (25.49%)
 * Likes:    2437
 * Dislikes: 3788
 * Total Accepted:    801.8K
 * Total Submissions: 3.1M
 * Testcase Example:  '123'
 *
 * 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: [−2^31,  2^31 − 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)
    {
        long long y = 0;
        for (; x; x /= 10)
            y = y * 10 + x % 10;
        if (y < -2147483648ll || y > 2147483647ll) y = 0;
        return y;
    }
};