Shuffle the Array 1470

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

Intuition

• A single loop did not work.
• By using two pointers — one for each half we can alternately pick elements and construct the required order efficiently.

Approach

• Create a new array result of size 2 * n.
• Initialize two pointers:
  • p1 = 0 to traverse the first half of nums
  • p2 = n to traverse the second half of nums
• Initialize an index i = 0 for the result array.
• While both pointers are within bounds:
  • Assign nums[p1] and nums[p2] alternately to result
  • Increment p1, p2, and i accordingly.
• Return the result array.

Complexity

• Time complexity:

• O(n)

• Space complexity:
• O(n)

Code

java [] class Solution { public int[] shuffle(int[] nums, int n) { int[] result=new int[2*n]; int p1=0; int p2=n; int i=0; while(p1<n && p2<2*n){ result[i++]=nums[p1++]; result[i++]=nums[p2++]; } return result; } }