Description
Given an array nums, write a function to move all 0’s to the end of it while maintaining the relative order of the non-zero elements.
Example:
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Input: [0,1,0,3,12]
Output: [1,3,12,0,0]
Note:
- You must do this in-place without making a copy of the array.
- Minimize the total number of operations.
Approach 1
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class Solution:
def moveZeroes(self, nums: List[int]) -> None:
"""
Do not return anything, modify nums in-place instead.
"""
i = 0
while True:
if 0 in nums:
nums.remove(0)
i += 1
else:
break
nums += [0] * i
Keep removing and counting all 0 from list, then add those number of 0 back to the list. The simplest logic, but not efficient, because it has to check if there is 0 left in the array every time, and this check has time complexity of O(N) and method remove has the same complexity.
Runtime: 188 ms, faster than 17.12% of Python3 online submissions for Move Zeroes.
Memory Usage: 14.9 MB, less than 5.97% of Python3 online submissions for Move Zeroes.
Approach 2
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class Solution:
def moveZeroes(self, nums: List[int]) -> None:
"""
Do not return anything, modify nums in-place instead.
"""
counter = 0
for i in range(len(nums)):
if nums[i-counter] == 0:
nums.pop(i-counter)
counter += 1
nums += [0] * counter
Runtime: 52 ms, faster than 52.77% of Python3 online submissions for Move Zeroes.
Memory Usage: 15 MB, less than 5.97% of Python3 online submissions for Move Zeroes.
Time efficiency improved a lot, because we omitted the if element in nums check in line 9, but the overall logic stays the same.
