LeetCode重点题系列之【75. 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]

This problem can be solved by Rainbow Sort algorithm. We should maintain three pointers, left, cur, right. Left pointer means the element before it is all 0, the element between left and right means uncertain elements. The element after right pointer means the element is all 2. Cur is the traverse pointer.

class Solution(object):
    def sortColors(self, nums):
        """
        :type nums: List[int]
        :rtype: void Do not return anything, modify nums in-place instead.
        """
        cur,l,r=0,0,len(nums)-1
        while cur<=r:
            if nums[cur]==0:
                nums[l],nums[cur]=nums[cur],nums[l]
                cur+=1
                l+=1
            elif nums[cur]==2:
                nums[cur],nums[r]=nums[r],nums[cur]
                r-=1
            else:
                cur+=1