Leetcode: Wiggle Sort

Question

Given an unsorted array nums, reorder it in-place such that nums[0] <= nums[1] >= nums[2] <= nums[3]….

For example, given nums = [3, 5, 2, 1, 6, 4], one possible answer is [1, 6, 2, 5, 3, 4].

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Solution

Get idea from here.

class Solution(object):
    def wiggleSort(self, nums):
        """ :type nums: List[int] :rtype: void Do not return anything, modify nums in-place instead. """

        if nums==None or len(nums)==0:
            return 

        flag = True   # flag=True means current elem is smaller than next one, otherwise false
        cur = nums[0]
        for ind in range(len(nums)-1):
            if (flag and cur>nums[ind+1]) or (not flag and cur<nums[ind+1]):
                nums[ind] = nums[ind+1]
            else:
                nums[ind] = cur
                cur = nums[ind+1]
            flag = not flag

        nums[-1] = cur

Consider the case: [ 2, 6, 4, 5, 3]