Subject description:
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:
- A rather straight forward solution is a two-pass algorithm using counting sort.
First, iterate the array counting number of 0's, 1's, and 2's, then overwrite array with total number of 0's, then 1's and followed by 2's. - Could you come up with a one-pass algorithm using only constant space?
Code:
1 def sortColors(self, nums): 2 i = j = 0 3 for k in xrange(len(nums)): 4 v = nums[k] 5 nums[k] = 2 6 if v < 2: 7 nums[j] = 1 8 j += 1 9 if v == 0: 10 nums[i] = 0 11 i += 1