#75 Sort Colors——Top 100 Liked Questions

短命女 2022-01-29 03:41 328阅读 0赞

Given an array with *n* objects colored red, white or blue, sort them **[in-place][] **so that objects of the same color are adjacent, with the colors in the order red, white and blue.

Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue respectively.

**Note:** You are not suppose to use the library's sort function for this problem.

**Example:**

Input: [2,0,2,1,1,0]
    Output: [0,0,1,1,2,2]

> """
> 
> 第一次：采用三个指针left=0负责0，cur=0，right=len(nums)-1 负责2，依次遍历nums，如果cur是0，与left交换， 并且left+1，cur+1，如果cur是2，right-1，如果cur是1，cur+1  
> """
> 
>     class Solution(object):
>         def sortColors(self, nums):
>             """
>             :type nums: List[int]
>             :rtype: None Do not return anything, modify nums in-place instead.
>             """
>             if not nums:
>                 return None
>             left = 0
>             right = len(nums) - 1
>             cur = 0
>             while cur <= right:
>                 if nums[cur] == 0:
>                     nums[cur], nums[left] = nums[left], nums[cur]
>                     left += 1
>                     cur += 1
>                 elif nums[cur] == 2:
>                     nums[cur], nums[right] = nums[right], nums[cur]
>                     right -= 1
>                 else:
>                     cur += 1
> 
> """
> 
> Runtime: 20 ms, faster than 96.31% of Python online submissions for Sort Colors.
> 
> Memory Usage: 11.7 MB, less than 81.67% of Python online submissions for Sort Colors.
> 
> """

[in-place]: https://en.wikipedia.org/wiki/In-place_algorithm