7.reverse-integer.java

/*
 * @lc app=leetcode id=7 lang=java
 *
 * [7] Reverse Integer
 *
 * https://leetcode.com/problems/reverse-integer/description/
 *
 * algorithms
 * Easy (25.14%)
 * Total Accepted:    653.5K
 * Total Submissions: 2.6M
 * 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 result = 0;
    while (x != 0) {
      result = result * 10 + x % 10;
      x = x / 10;
    }
    if (result > Integer.MAX_VALUE || result < Integer.MIN_VALUE) {
      return 0;
    }
    return (int)result;
  }
}