Sort an array of 0s, 1s and 2s

Given an array A[] consisting 0s, 1s and 2s, write a function that sorts A[]. The functions should put all 0s first, then all 1s and all 2s in last.

Example
Input = {0, 1, 1, 0, 1, 2, 1, 2, 0, 0, 0, 1};
Output = {0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2}

Solution:

    static void sort(int a[], int arr_size)

    {

        int lo = 0;

        int hi = arr_size - 1;

        int mid = 0,temp=0;

        while (mid <= hi)

        {

            switch (a[mid])

            {

            case 0:

            {

                temp   =  a[lo];

                a[lo]  = a[mid];

                a[mid] = temp;

                lo++; //increase low index

                mid++; //increase high index

                break;

            }

            case 1:

                mid++; //increase only middle index

                break;

            case 2:

            {

                temp = a[mid];

                a[mid] = a[hi];

                a[hi] = temp;

                hi--; //decrease high index

                break;

            }

            }

        }

    }