Practice/Oracle/Leetcode 7. Reverse Integer

Leetcode 7. Reverse Integer

CodingMust

Problem

Given a 32-bit signed integer, reverse its digits while preserving the sign. If reversing the digits causes the result to exceed the range of a 32-bit signed integer (from -2³¹ to 2³¹ - 1), return 0 instead.

Your solution must detect potential overflow conditions without relying on 64-bit integer types or larger data structures.

Requirements

1. Reverse the digits of the input integer
2. Preserve the original sign (positive or negative)
3. Return 0 if the reversed number would overflow a 32-bit signed integer
4. The overflow check must be performed without using 64-bit integers
5. Handle edge cases like numbers with trailing zeros

Constraints

• -2³¹ ≤ x ≤ 2³¹ - 1
• You cannot store the integer in a larger data type (no 64-bit integers)
• Time complexity should be O(log n) where n is the value of the input
• Space complexity should be O(1)

Examples

Example 1:

Input: x = 123 Output: 321 Explanation: Simply reverse the digits of the positive number.

Example 2:

Input: x = -456 Output: -654 Explanation: Reverse the digits while keeping the negative sign.

Example 3:

Input: x = 120 Output: 21 Explanation: After reversal, leading zeros are dropped.

Example 4:

Input: x = 1534236469 Output: 0 Explanation: The reversed number 9646324351 exceeds 2,147,483,647 (the maximum 32-bit signed integer), so we return 0.