//* find adjacent - iterators and standard algorithms *
#include <vector>
#include <iostream>
using namespace std;


template <typename iterator>
iterator adjacent_find(iterator beg, iterator data_end) {
    iterator found = data_end; // nothing found - return the data_end value iterator
    if (beg != data_end) {
        // we cannot proceed with ++ahead if data collection is empty
        iterator ahead = beg;
        ++ahead;

        for (iterator behind = beg; ahead != data_end; ++ahead, ++behind) {
            if (*ahead == *behind) {
                found = behind;
                //  OR found = ahead; - depends on what do you need
                break;
            }
        }
    }
    return(found);
}


template <typename iterator>
void print_all(iterator data_start, iterator data_end) {
    for (iterator scan = data_start; scan != data_end; ++scan)
        cout << ' ' << *scan;
    cout << endl;
}


// sample test program
int main() {
    // get a sample vector with some data
    vector<double> V;
    cout << "Please enter several values followed by the letter 's':" << endl;
    for (;;) {
        double x;
        cin >> x;
        if (cin.fail()) break;
        V.push_back(x);
    }
    cin.clear();
    cin.ignore(256, '\n');

    // do some testing
    vector<double>::iterator pos;
    pos = adjacent_find(V.begin(), V.end());
    if (pos == V.end())
        cout << "Adjacent equal values not found in this vector." << endl;
    else
        cout << "Adjacent equal values found! First pair equals " << *pos << endl;

    return(0);
}