Hi, here's your problem today. This problem was recently asked by Apple:

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.

Can you do this in a single pass?

Example:
Input: [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]
Here's a starting point:

<pre lang=py>
class Solution:
  def sortColors(self, nums):
    # Fill this in.

nums = [0, 1, 2, 2, 1, 1, 2, 2, 0, 0, 0, 0, 2, 1]
print("Before Sort: ")
print(nums)
# [0, 1, 2, 2, 1, 1, 2, 2, 0, 0, 0, 0, 2, 1]

Solution().sortColors(nums)
print("After Sort: ")
print(nums)
# [0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2]
</pre>