LeetCode-in-Ruby.github.io

75. Sort Colors

Medium

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]

Example 3:

Input: nums = [0]

Output: [0]

Example 4:

Input: nums = [1]

Output: [1]

Constraints:

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

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

Solution

# @param {Integer[]} nums
# @return {Void} Do not return anything, modify nums in-place instead.
def sort_colors(nums)
  l = 0
  h = nums.size - 1
  i = 0
  while i <= h
    if nums[i] == 2
      nums[i] = nums[h]
      nums[h] = 2
      h -= 1
    elsif nums[i] == 0
      nums[i] = nums[l]
      nums[l] = 0
      l += 1
      i += 1
    else
      i += 1
    end
  end
end

This site is open source. Improve this page.