Problem

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.

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

Constraints:

n == nums.length1 <= n <= 300nums[i] is 0, 1, or 2.

Follow up:

Could you solve this problem without using the library’s sort function?Could you come up with a one-pass algorithm using only O(1) constant space?

Example1

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

Example2

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

Example3

Input: nums = [0] Output: [0]

Example4

Input: nums = [1] Output: [1]

Solution

class Solution { public: void sortColors(vector<int>& nums) { int i = 0; int j = 0; int k = nums.size() - 1; while(i <= k) { if(nums[i] == 0) { swap(nums[i++],nums[j++]); } else if(nums[i] == 1) { ++i; } else{ swap(nums[i],nums[k--]); } } } };