sort color or sort 0 1 2

  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]

Optimal Approach (In place solve)

class Solution {
    // Swap elements at indices i and j in array arr
    public static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

    public void sortColors(int[] nums) {
        int l = 0;                 // low: next position for 0
        int m = 0;                 // mid: current element
        int h = nums.length - 1;   // high: next position for 2

        while (m <= h) {
            if (nums[m] == 0) {
                swap(nums, l, m);
                l++;
                m++;
            } else if (nums[m] == 1) {
                m++;
            } else if (nums[m] == 2) {
                swap(nums, m, h);
                h--; // do not increment m, because swapped value at m needs checking
            }
        }
    }
}


BruteForce :-

class Solution {
    public void sortColors(int[] nums) {
       
        int n=nums.length;
int count0=0,count1=0,count2=0;
        for(int i=0;i<n;i++)
        {
if(nums[i]==0)
{
    count0++;
}
        }
       
        for(int i=0;i<n;i++)
        {
            if(nums[i]==1)
{
    count1++;
}
        }
       
        for(int i=0;i<n;i++)
        {
            if(nums[i]==0)
{
    count2++;
}
        }


        for(int i=0;i<count0;i++)
        {
            nums[i]=0;
        }
        for(int i=count0;i<count0+count1;i++)
        {
             nums[i]=1;
        }

        for(int i=count0+count1;i<n;i++)
        {
             nums[i]=2;
        }
       
    }
}

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