Use mismatch function to find the first match : mismatch « STL Algorithms Non modifying sequence operations « C++ Tutorial

1. C++ Tutorial
2. STL Algorithms Non modifying sequence operations
3. mismatch

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */

#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#include <numeric>

/* PRINT_ELEMENTS()
 * - prints optional C-string optcstr followed by
 * - all elements of the collection coll
 * - separated by spaces
 */
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
    typename T::const_iterator pos;

    std::cout << optcstr;
    for (pos=coll.begin(); pos!=coll.end(); ++pos) {
        std::cout << *pos << ' ';
    }
    std::cout << std::endl;
}

/* INSERT_ELEMENTS (collection, first, last)
 * - fill values from first to last into the collection
 * - NOTE: NO half-open range
 */
template <class T>
inline void INSERT_ELEMENTS (T& coll, int first, int last)
{
    for (int i=first; i<=last; ++i) {
        coll.insert(coll.end(),i);
    }
}

using namespace std;

int main()
{
    vector<int> coll1;
    list<int> coll2;

    INSERT_ELEMENTS(coll1,1,6);

    for (int i=1; i<=16; i*=2) {
        coll2.push_back(i);
    }
    coll2.push_back(3);

    PRINT_ELEMENTS(coll1,"coll1: ");
    PRINT_ELEMENTS(coll2,"coll2: ");

    // find first mismatch
    pair<vector<int>::iterator,list<int>::iterator> values;
    values = mismatch (coll1.begin(), coll1.end(),  // first range
                       coll2.begin());              // second range
    if (values.first == coll1.end()) {
        cout << "no mismatch" << endl;
    }
    else {
        cout << "first mismatch: "
             << *values.first  << " and "
             << *values.second << endl;
    }

}

coll1: 1 2 3 4 5 6
coll2: 1 2 4 8 16 3
first mismatch: 3 and 4