7.ReverseInteger.md

7. Reverse Integer

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

Note:

Assume we are dealing with an environment that 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.

Example 1:

Input: x = 123
Output: 321

Example 2:

Input: x = -123
Output: -321

Example 3:

Input: x = 120
Output: 21

Example 4:

Input: x = 0
Output: 0

Constraints:

• -231 <= x <= 231 - 1

Solution

• java

/*
  Success Detail:
  Runtime: 1 ms, faster than 100.00% of Java online submissions for Reverse Integer.
  Memory Usage: 35.9 MB, less than 80.80% of Java online submissions for Reverse Integer.      
 */
class Solution {
    public int reverse(int x) {
        int num = 0;
        while (x != 0) {
            if ((num == Integer.MAX_VALUE / 10 && x % 10 > 8) || num > Integer.MAX_VALUE / 10) {
                return 0;
            }

            if ((num == Integer.MIN_VALUE / 10 && x % 10 > 7) || num < Integer.MIN_VALUE / 10) {
                return 0;
            }

            num = num * 10 + x % 10;
            x /= 10;
        }
        return num;
    }
}