find() and count ()

/************ stack.h ************/
#include<vector>
#include<iostream>
#include<algorithm>
using namespace std;
class stack
{
    public:
    bool push(const string&);
    bool pop(string &elem);
    bool peek(string &elem);
    bool empty() const {return _stack.empty();}
    bool full() const {return _stack.size()==_stack.max_size();}
    int size() const {return _stack.size();}
    bool find(const string &elem) const;
    int count(const string &elem) const;

    private:
    vector<string> _stack;

};

/********** stack.cpp **********/

#include "stack.h"
bool stack::push(const string& str)
{
    if(full()) return false;
    _stack.push_back(str);
    return true;
}
bool stack::pop(string& elem)
{
    if(empty()) return false;
    elem = _stack.back();
    _stack.pop_back();
    return true;
}
bool stack::peek(string& elem)
{
    if(empty()) return false;
    elem = _stack.back();
    return true;
}
bool stack::find (const string &elem) const
{
    vector<string>::const_iterator it = _stack.begin();
    return (::find(it,_stack.begin(),elem))!=_stack.end();
}
int stack::count(const string &elem) const
{

    return (::count(_stack.begin(),_stack.end(),elem));
}

/*********** main.cpp *************/
#include "stack.cpp"
#include<fstream>
int main()
{
    stack st;
    string str;
    ifstream readfile("sentence.txt");
    while(readfile>>str && !st.full())
    {
        st.push(str);
    }
    if (st.empty())
    {
        cout<<"Oops! No strings were read\n";
        return 0;
    }
    st.peek(str);
    if (st.size()==1 && str.empty())
    {
        cout<<"Oops! No strings were read\n";
        return 0;
    }
    cout<<"The number of elements read are: "<<st.size()<<endl;
    cout<<"The sentence in reverse order is: "<<endl;
    while(!st.empty())
    {
        st.pop(str);
        cout<<str<<' ';
    }
    cout<<"\nEnter a word to search: ";
    cin>>str;
    if(st.find(str))
        cout<<"The word was found "<<st.count(str)<<" no. of times"<<endl;
    else
        cout<<"The word was not found"<<endl;
    return 0;

}