Common elements.cpp

#include <bits/stdc++.h>
using namespace std;
class Solution
{
    public:    
       vector <int> commonElements (int A[], int B[], int C[], int n1, int n2, int n3)
        {
    
              vector<int> result;
    int i = 0, j = 0, k = 0;

    while (i < n1 && j < n2 && k < n3) {
        if (A[i] == B[j] && B[j] == C[k]) {
            // Found a common element
            result.push_back(A[i]);
            // Move all pointers to the next different element
            int current = A[i];
            while (i < n1 && A[i] == current) i++;
            while (j < n2 && B[j] == current) j++;
            while (k < n3 && C[k] == current) k++;
        } else {
            // Move pointers of arrays with smaller values
            if (A[i] <= B[j] && A[i] <= C[k]) i++;
            else if (B[j] <= A[i] && B[j] <= C[k]) j++;
            else if (C[k] <= A[i] && C[k] <= B[j]) k++;
        }
    }

    return result;
        }

};
int main ()
{
    int t; cin >> t;
    while (t--)
    {
        int n1, n2, n3; 
        cin >> n1 >> n2 >> n3;
        int A[n1];
        int B[n2];
        int C[n3];
        
        for (int i = 0; i < n1; i++) cin >> A[i];
        for (int i = 0; i < n2; i++) cin >> B[i];
        for (int i = 0; i < n3; i++) cin >> C[i];
        
        Solution ob;
        
        vector <int> res = ob.commonElements (A, B, C, n1, n2, n3);
        if (res.size () == 0) 
            cout << -1;
        for (int i = 0; i < res.size (); i++) 
            cout << res[i] << " "; 
        cout << endl;
    }
}