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LC1470 - Shuffle the Array

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Datastructure and Algorithm: DAY 90. Leetcode: 286/2752

Description

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:

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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:

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

Example 3:

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

Constraints:

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

Solution

  1. slow index: i, faster index: j
    • initial i = 0, j = n
  2. when j reaches to the end, i reaches the end of the first half of this array
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# O(n) time | O(n) space
class Solution:
    def shuffle(self, nums: List[int], n: int) -> List[int]:
        i, j = 0, n
        ans = []
        for j in range(n, len(nums)):
            ans.append(nums[i])
            ans.append(nums[j])
            i += 1
        return ans