Reverse Integer

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Problem

Given a signed 32-bit integer, reverse its digits. If reversing causes the value to fall outside the signed 32-bit integer range, return 0.

Examples

Example 1

Input:x = 123

Output:321

Example 2

Input:x = -123

Output:-321

Constraints

-2^31 <= x <= 2^31 - 1

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How to approach it: the Bit Manipulation pattern

Work directly on a number's binary representation using bitwise operators — often turning an O(n) or O(log n) problem into a handful of O(1) operations.

Look for this pattern when

The problem talks about bits directly (count set bits, reverse bits, single number among duplicates).
You want a constant-time trick instead of a loop for a numeric problem.

Read the full Bit Manipulation guide →

Video walkthroughs

Original problem on LeetCode ↗