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]
Follow up:
这个题目就是像利用quick sort，设一个mid，然后利用two pointers分别将小于等于mid的放到左边，大于mid的放到右边，先将0放在左边，然后再将mid设为1用一遍，即可。
Code
class Solution: def sortColors(self, nums): """ Do not return anything, modify nums in-place instead. """ def divideMid(nums, start, end, mid): while start <= end: while start <= end and nums[start] <= mid: start += 1 while start <= end and nums[end] > mid: end -= 1 if start <= end: nums[start], nums[end] = nums[end], nums[start] start += 1 end -= 1 return start n = len(nums) index = divideMid(nums, 0, n - 1, 0) divideMid(nums, index, n - 1, 1)
[LeetCode] 75. Sort Colors_Medium tag: Two pointers
原文：https://www.cnblogs.com/Johnsonxiong/p/10851273.html