C++ Tutorial/STL Algorithms Non modifying sequence operations/search n

search the vector for the occurrence of a certain pattern with search_n

<source lang="cpp">#include <algorithm>

1. include <vector>
2. include <list>
3. include <iostream>

using namespace std; int main () {

   vector <int> v;
   for (int nNum = -9; nNum < 10; ++ nNum)
       v.push_back (nNum);
   v.push_back (9);
   v.push_back (9);
   list <int> l;
   for (int nNum = -4; nNum < 5; ++ nNum)
       l.push_back (nNum);
   // search the vector for the occurrence of pattern {9, 9, 9}
   vector <int>::iterator vl;
   vl = search_n ( v.begin () // Start range
                 , v.end ()   // End range
                 , 3          // Count of item to be searched for
                 , 9 );       // Item to search for
   if (vl != v.end ()){
       cout << "The sequence {9, 9, 9} found a match in the vector at ";
       cout << "offset-position: ";
       cout << distance (v.begin (), vl);
       cout << endl;
   }
   return 0;

}</source>

Use search_n to find four consecutive elements with value 3

<source lang="cpp">/* 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.
*/

1. include <iostream>
2. include <vector>
3. include <deque>
4. include <list>
5. include <set>
6. include <map>
7. include <string>
8. include <algorithm>
9. include <iterator>
10. include <functional>
11. 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() {

  deque<int> coll;
  INSERT_ELEMENTS(coll,1,9);
  PRINT_ELEMENTS(coll);
  // find four consecutive elements with value 3
  deque<int>::iterator pos;
  pos = search_n (coll.begin(), coll.end(),    // range
                  4,                           // count
                  3);                          // value
  // print result
  if (pos != coll.end()) {
      cout << "four consecutive elements with value 3 "
           << "start with " << distance(coll.begin(),pos) +1
           << ". element" << endl;
  }
  else {
      cout << "no four consecutive elements with value 3 found"
           << endl;
  }

}</source>

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no four consecutive elements with value 3 found

Use search_n with custom function to find four consecutive elements with value greater than 3

<source lang="cpp">/* 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.
*/

1. include <iostream>
2. include <vector>
3. include <deque>
4. include <list>
5. include <set>
6. include <map>
7. include <string>
8. include <algorithm>
9. include <iterator>
10. include <functional>
11. 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() {

  deque<int> coll;
  INSERT_ELEMENTS(coll,1,9);
  PRINT_ELEMENTS(coll);
  deque<int>::iterator pos;
  // find four consecutive elements with value greater than 3
  pos = search_n (coll.begin(), coll.end(),    // range
                  4,                           // count
                  3,                           // value
                  greater<int>());             // criterion
  // print result
  if (pos != coll.end()) {
           << "start with " << distance(coll.begin(),pos) +1
           << ". element" << endl;
  }
  else {
           << endl;
  }

}</source>

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four consecutive elements with value > 3 start with 4. element