Sort Colors

Problem Description

Given an array nums 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.

We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.

You must solve this problem without using the library's sort function.

Example 1:

Input: nums = [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]

Example 2:

Input: nums = [2,0,1]
Output: [0,1,2]

Constraints:

• n == nums.length
• 1 <= n <= 300
• nums[i] is either 0, 1, or 2.

Follow up: Could you come up with a one-pass algorithm using only constant extra space?

Solution (Go)

func sortColors(nums []int) {
	var red, white int
	blue := len(nums) - 1
	for white <= blue {
		if nums[white] == 0 {
			nums[red], nums[white] = nums[white], nums[red]
			red += 1
			white += 1
		} else if nums[white] == 1 {
			white += 1
		} else {
			nums[blue], nums[white] = nums[white], nums[blue]
			blue -= 1
		}
	}
}