STL algorithm function templates

The program has to finds an element in a sorted array and implement this function template:

bool find(T *p, T value, int &index=null)
 

I have completed a part, but when I try to do the Null part all my number goes to zeros. Also I do not know how to implement the index. Can someone help me please.

int main()
 {
     vector<int> numbers;
     vector<int>::iterator iter;
 
     for (int x = 0; x < 15; x++)
         numbers.push_back(x);
 
     cout << "The numbers in the vector are:\n";
     for (iter = numbers.begin(); iter != numbers.end(); iter++)
         cout << *iter << " ";
     cout << endl << endl;
 
     iter = find(numbers.begin(), numbers.end(), 5);
     cout << *iter << endl;
 

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