0007-reverse-integer

Reverse Integer

Problem Link

Details

Difficulty: Medium
Topics: Math

Problem

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.

Assume the environment does not allow you to store 64-bit integers (signed or unsigned).

Examples

Example 1

Input: x = 123
Output: 321

Example 2

Input: x = -123
Output: -321

Example 3

Input: x = 120
Output: 21

Submission

Language: java
Runtime: 1 ms (99.98%)
Memory: 40.5 MB (78.70%)
Submitted: 2026-06-01

Solution

class Solution {
    public int reverse(int x) {
        int rev = 0;

        while (x != 0) {
            int digit = x % 10;

            if (rev > Integer.MAX_VALUE / 10 || (rev == Integer.MAX_VALUE / 10 && digit > 7)) return 0;
            if (rev < Integer.MIN_VALUE / 10 || (rev == Integer.MIN_VALUE / 10 && digit < -8)) return 0;

            rev = rev * 10 + digit;
            x /= 10;
        }

        return rev;
    }
}

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