common_elements_in_3_sorted_array.cpp

class Solution
{
    public:    
    vector <int> commonElements (int A[], int B[], int C[], int n1, int n2, int n3)
    {
        vector<int> res;
        
        int i = 0, j = 0, k = 0;
        
        while(i < n1 and j < n2 and k < n3)
        {
            while(i > 0 and i < n1 and A[i - 1] == A[i])
            {
                i++;
            }
            
            while(j > 0 and j < n2 and B[j - 1] == B[j])
            {
                j++;
            }
            
            while(k > 0 and k < n3 and C[k - 1] == C[k])
            {
                k++;
            }
            
            if(i < n1 and j < n2 and k < n3)
            {
                if(A[i] == B[j] and B[j] == C[k])
                {
                    res.push_back(A[i]);
                    
                    i++;
                    j++;
                    k++;
                }
                else if(A[i] < B[j])
                {
                    i++;
                }
                else if(B[j] < C[k])
                {
                    j++;
                }
                else
                {
                    k++;
                }
            }
        }
        
        return res;
    }
};