# LeetCode Problem 7. Reverse Integer

### Table Of Content

## Problem

Given a 32-bit signed integer, reverse digits of an integer.

```
Example 1:
Input: 123Output: 321Example 2:
Input: -123Output: -321Example 3:
Input: 120Output: 21
```

Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−2^31, 2^31 − 1]. For the purpose of this problem, assume that your function **returns 0 when the reversed integer overflows**.

## Solution

```
var reverse = function(x) { var isNegative = false if(x < 0) { isNegative = true } const str = Math.abs(x).toString()
if(str.length === 1) { return x } var revStr = "" const len = str.length for(var i = len - 1; i >= 0 ; i--) { revStr += str[i] } const reverseNum = +revStr if (reverseNum > 0x7FFFFFFF) { return 0 } return isNegative ? -reverseNum : reverseNum };
```

## Explanation

The input is a signed integer

Max 32 bit signed integer is But more efficient is using constant - 0x7FFFFFFF

Can it be converted to string and then converted back to integer

I bet this has some easy solution using bit manipulation But i hate bit manipulation

Let s go ahead with converting to string and back to integer We can maintain the sign in a variable

If the number is single digit we can just return it

`Math.abs(x)`

is important because we are maintaining the sign separately

`+revStr`

is a cool trick to convert string back to integer

`str.reverse()`

can make this much more cleaner. But, I like to write my own logic for reverse. It's better to do it this way in the interviews.

## Highlights

**Runtime:** 84 ms, faster than 75.52% of JavaScript online submissions for Reverse Integer.

**Memory Usage:** 37.7 MB, less than 14.63% of JavaScript online submissions for Reverse Integer.

### Disclaimer

This may not be the optimal solution. And that's okay. The purpose here is to practice problem solving and have fun with algorithms. I am constantly learning new optimized solutions for these problems.

Please comment below if you have a better solution. Let's learn algorithms and data structures together.

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