Reverse Integer

• 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).**

**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

**Note that if the negative number in, (-) sign goes to the left.**

• -5623 👉 3265- : 🙅‍♀️
• -5623 👉 -3265 : 🙆‍♂️

0x7FFFFFFF : a hexadecimal number that represents the maximum positive value for a 32-bit number

0x80000000 : a hexadecimal number that represents the minimum negative value for a 32-bit number

Start Quokka

Milestone

• check whether the number is negative / add a flag
• make absolute value the number
• turn the number into a string
• reverse it
• turn back the string into a number
• return

First attempt

First attempt

Refactor the code above using modular arithmetic

Refactoring

Reference

• https://leetcode.com/problems/reverse-integer/