Leetcode solution-Sort Colors .Dutch National Flag problem

Dutch_flag_prblm_on_leetcode.py

```python3 
#https://en.wikipedia.org/wiki/Dutch_national_flag_problem
#https://leetcode.com/problems/sort-colors/
def sortColors(self, nums):
    red, white, blue = 0, 0, len(nums)-1
    
    while white <= blue:
        if nums[white] == 0:
            nums[red], nums[white] = nums[white], nums[red]
            white += 1
            red += 1
        elif nums[white] == 1:
            white += 1
        else:
            nums[white], nums[blue] = nums[blue], nums[white]
            blue -= 1
 ```