[LC] 7. Reverse Integer

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.

Solution 1: comparison to handle overflow

class Solution {

    public int reverse(int x) {

        int res = 0;

        while (x != 0) {

            int cur = res;

            res = 10 * res + x % 10;

            if (cur != res / 10) {

                return 0;

            }

            x /= 10;

        }

        return res;

    }

}

Solution 2: use Long to handle overflow

class Solution {

    public int reverse(int x) {

        long res = 0;

        while (x != 0) {

            res = 10 * res + x % 10;

            if (res > Integer.MAX_VALUE || res < Integer.MIN_VALUE) {

                return 0;

            }

            x /= 10;

        }

        return (int)res;

    }

}

巴特西

[LC] 7. Reverse Integer

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