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LeetCode 1470 Shuffle The Array - Easy

1470. Shuffle the Array -- Easy

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1470. Shuffle The Array — Easy

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Problem

  1. Shuffle the Array -- Easy

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

Solution

# generator:
class Solution:
    def shuffle(self, nums: List[int], n: int) -> List[int]:
        def gen(A):
            for i in range(n): 
                yield from (A[i], A[i+n])
        return list(gen(nums))
        
# O(N), O(1), by marking:
class Solution:
    def shuffle(self, nums: List[int], n: int) -> List[int]:
        getDesireIdx = lambda i: i*2 if i<n else (i-n)*2+1
        for i in range(2*n):
            j=i
            while nums[i]>=0:
                j=getDesireIdx(j)
                nums[i],nums[j]=nums[j],-nums[i]
        for i in range(2*n):
            nums[i]=-nums[i]
        return nums

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