Leetcode.283 Move Zeroes

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:

Input: [0,1,0,3,12]
Output: [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

移位置零

• 填充
• 移位
• 置零

class Solution:
    def moveZeroes(self, nums: list[int]) -> None:
        """
        填充，移位，置零
        """
        # j指向非0數字將要插入的位置
        j = 0
        n = len(nums)
        for i in range(n):
            if nums[i] != 0:
                nums[j] = nums[i]
                j += 1

        for i in range(j, n):
            nums[i] = 0
 

快慢指標

利用一個指標指向列表第一個0，尋找之後非零數字與其交換

class Solution:
    def moveZeroes(self, nums: List[int]) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        if not nums:
            return nums
        
        zero = 0
        n = len(nums)
        # zero point first 0
        while zero<n and nums[zero]!=0:
            zero+=1
        
        i = zero +1
        while i<n:
            if nums[i] != 0:
                nums[zero],nums[i] = nums[i],nums[zero]
                zero+=1
            i+=1