Day15_SortColors.cpp

// 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?

// Topics
// Array
// Two Pointers
// Sorting


// Solutions:


class Solution {
public:
    void sortColors(vector<int>& nums) {
        int n=nums.size();
        int zero=0,one=0,two=0;
        for(int i=0;i<n;i++){
            if(nums[i]==0){zero++;}
            else if(nums[i]==1){one++;}
            else{two++;}
        }
        int i=0;
        while(zero-->0){
            nums[i]=0;
            i++;
        }
        while(one-->0){
            nums[i]=1;
            i++;
        }
        while(two-->0){
            nums[i]=2;
            i++;
        }

    }
};