1470. Shuffle the Array

EasyLeetCode

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].

Example 1:

Input: nums = [2,5,1,3,4,7], n = 3 Output: [2,3,5,4,1,7] Explanation: Since x1=2, x2=5, x3=1, y1=3, y2=4, y3=7 then the answer is [2,3,5,4,1,7].

Example 2:

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

Example 3:

Input: nums = [1,1,2,2], n = 2 Output: [1,2,1,2]

Constraints:

• 1 <= n <= 500
• nums.length == 2n
• 1 <= nums[i] <= 10^3

How to solve the problem

There are two approaches to solve this problem:

1. Pre-allocate space for array result

2.Build the result array by appending elements one by one.

Code

Pre-allocate space for array result and fill it using index calculation.

class Solution:
    def shuffle(self, nums: List[int], n: int) -> List[int]:
        result = [0] * (2 * n)
        for i in range(n):
            result[2 * i] = nums[i]
            result[2 * i + 1] = nums[i + n]
        return result

Build the result array by appending elements one by one.

class Solution:
    def shuffle(self, nums: List[int], n: int) -> List[int]:
        result = []
        for i in range(n):
            result.append(nums[i])
            result.append(nums[i + n])
        return result

Complexity

Time complexity: O(n)

• One for loop that iterates n times.

Space complexity: O(n)

• One-dimensional array of size 2n.