Sort Colors

最新推荐文章于 2019-09-27 09:24:00 发布

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最新推荐文章于 2019-09-27 09:24:00 发布

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分类专栏： leetcode 文章标签： leetcode python

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Sort Colors

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]

Solution

@允许两次遍历的话就直接对0、1、2计数再依次填充即可，一次遍历设定双指针
class Solution:
    def sortColors(self, nums: List[int]) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        if nums==[]:
            return nums
        p1 = 0
        p2 = len(nums)-1
        i  = 0
        while i<=p2:
            if nums[i]==2:
                nums[i], nums[p2] = nums[p2], 2
                p2 -= 1
            elif nums[i]==0:
                nums[i], nums[p1] = nums[p1], 0
                p1 += 1
                i += 1
            else:
                i += 1