283.Move Zeroes

Tags: [overriding], [pointers]

Link: https://leetcode.com/problems/move-zeroes/#/description

Given an arraynums, write a function to move all0's to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function,numsshould be[1, 3, 12, 0, 0].

Note:

1. You must do this in-place without making a copy of the array.
2. Minimize the total number of operations.

Solution: Overriding

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

        real_end = 0
        for n in nums:
            if n:
                nums[real_end] = n
                real_end += 1

        while real_end < len(nums):
            nums[real_end] = 0
            real_end += 1

Revelation:

• Overriding the positions at where its original elements are 0s.

Note:

• Time complexity = O(n), n is the number of elements of the given nums.

Solution: Pointers

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

        end = len(nums) - 1
        index = len(nums) - 1

        while index >= 0:
            if nums[index] == 0:
                for i in xrange(index + 1, end + 1):
                    nums[i - 1] = nums[i]

                nums[end] = 0
                end -= 1

            index -= 1

Note:

• Time complexity = O(n^2), n is the number of elements in the given nums.