Leetcode 75. Sort Colors

https://leetcode.com/problems/sort-colors/

If we set two pointers, p0 and p2 to indicate the supposed position of 0 and 2, the left 1 will be in the middle automatically.

Solution:

# T:O(n) S:O(1)
class Solution:
    # @param {integer[]} nums
    # @return {void} Do not return anything, modify nums in-place instead.
    def sortColors(self, nums):
        L = len(nums)
        p0, p2, i = 0, L - 1, 0
        while i <= p2:
            if nums[i] == 2:
                nums[i], nums[p2] = nums[p2], nums[i]
                p2 -= 1
            elif nums[i] == 0:
                nums[i], nums[p0] = nums[p0], nums[i]
                p0 += 1
                i += 1
            else:
                i += 1

Run Time: 56 ms