This post is part of the Algorithms Problem Solving series.

## Problem description

This is the Shuffle the array problem. The description looks like this:

Given the array `nums`

consisting of `2n`

elements in the form `[x1,x2,...,xn,y1,y2,...,yn]`

.

*Return the array in the form* `[x1,y1,x2,y2,...,xn,yn]`

.

## Examples

```
Input: nums = [2,5,1,3,4,7], n = 3
Output: [2,3,5,4,1,7]
Input: nums = [1,2,3,4,4,3,2,1], n = 4
Output: [1,4,2,3,3,2,4,1]
Input: nums = [1,1,2,2], n = 2
Output: [1,2,1,2]
```

## Solution

The idea of my solution was to get the first and the last half of the `nums`

list. Then iterate through the lists and append one by one.

```
def shuffle(nums, n):
first_half = nums[:n]
last_half = nums[n:]
final_list = []
for index in range(len(first_half)):
final_list.append(first_half[index])
final_list.append(last_half[index])
return final_list
```

We could also iterate through the lists simultaneously by using the `zip`

function. And append the items in one call, instead of two lines:

```
def shuffle(nums, n):
first_half = nums[:n]
last_half = nums[n:]
final_list = []
for first, last in zip(first_half, last_half):
final_list.extend((first, last))
return final_list
```

## Top comments (1)

Not sure if this is idiomatic Python but we can do it in O(n) space and O(log(n)) time ... I think ... :-)