Use find to search an element in a container : find « STL Algorithms Non modifying sequence operations « C++ Tutorial

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

/* 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()
{
    list<int> coll;

    INSERT_ELEMENTS(coll,1,9);
    INSERT_ELEMENTS(coll,1,9);

    PRINT_ELEMENTS(coll,"coll: ");

    // find first element with value 4
    list<int>::iterator pos1;
    pos1 = find (coll.begin(), coll.end(),    // range
                 4);                          // value

    /* find second element with value 4
     * - note: continue the search behind the first 4 (if any)
     */
    list<int>::iterator pos2;
    if (pos1 != coll.end()) {
        pos2 = find (++pos1, coll.end(),      // range
                     4);                      // value
    }

    /* print all elements from first to second 4 (both included)
     * - note: now we need the position of the first 4 again (if any)
     * - note: we have to pass the position behind the second 4 (if any)
     */
    if (pos1!=coll.end() && pos2!=coll.end()) {
        copy (--pos1, ++pos2,
              ostream_iterator<int>(cout," "));
        cout << endl;
    }
}

coll: 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
4 5 6 7 8 9 1 2 3 4