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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]
这道题第一个想法就是sort,当然题目说不要用sort,而且使用one-pass的方法,遍历一遍且inplace解决
思路:
使用index记录0和2的位置,0位置初始化为0,2为位置初始化为len-1
遍历到0或2就挪动交换到指示的位置
class Solution(object):
def sortColors(self, nums):
"""
:type nums: List[int]
:rtype: void Do not return anything, modify nums in-place instead.
"""
#1 sort
#2 record index
idx_0 = 0
idx_2 = len(nums) - 1
idx = 0
while(idx < len(nums)):
if nums[idx] == 0 and idx_0 < idx:
nums[idx_0],nums[idx] = nums[idx],nums[idx_0]
idx_0 += 1
elif nums[idx] == 2 and idx_2 > idx:
nums[idx_2],nums[idx] = nums[idx],nums[idx_2]
idx_2 -= 1
else:idx += 1