Linked list finding first recurring integer!

#include <iostream>
#include <vector>
using namespace std;

class HashTables{
    public:
        
        
        static const int TableSize = 10;
        int Table[TableSize];
        HashTables()
        {
            for(int i = 0; i < TableSize; i ++)
            {
                Table[i] = 0;
            }
        }
            
        void recurring(vector<int> arr)
        {
            int i; 
            for(i = 0 ; i < arr.size(); i ++)
            {
                if(Table[arr[i]] == 1){
                    cout << arr[i];
                    return;
                }
                if(Table[arr[i]] < 2)
                    Table[arr[i]]++;
                
            }
            if(i == arr.size()){
                cout << "undefined";
            }
        }
        
};

int main() {
    vector<int> One = {2,5,1,2,3,5,1,2,4};
    vector<int> Two = {2,1,1,2,1,3,5,1,2,4};
    vector<int> Three = {2,3,4,5};
    
    HashTables Find;
    
    Find.recurring(Three);
    return 0;
}