75. Sort Colors

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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?

Accepted
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Submissions
2.3M
Acceptance Rate
58.2%

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class Solution {
public:
    void sortColors(vector<int>& nums) {
      int low=0;
      int high=nums.size()-1;
      int mid=0;

      while(mid<=high){
          switch (nums[mid]){

              case 0: 
              swap(nums[low++], nums[mid++]);
              break;

              case 1: 
              mid++;
              break;

              case 2: 
              swap(nums[mid], nums[high--]);
              break; 
          }
      }  

    }
};