C++/STL Algorithms Non modifying sequence operations/mismatch

Check for mismatch between two vectors

<source lang="cpp">

1. include <iostream>

using std::cout; using std::endl;

1. include <algorithm>
2. include <vector>
3. include <iterator>

int main() {

  int a1[ 10 ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
  int a2[ 10 ] = { 1, 2, 3, 4, 9, 6, 7, 8, 9, 10 };
  std::vector< int > v1( a1, a1 + 10 );
  std::vector< int > v2( a1, a1 + 10 );
  std::vector< int > v3( a2, a2 + 10 );
  std::ostream_iterator< int > output( cout, " " );
  cout << "Vector v1 contains: ";
  std::copy( v1.begin(), v1.end(), output );
  cout << "\nVector v2 contains: ";
  std::copy( v2.begin(), v2.end(), output );
  cout << "\nVector v3 contains: ";
  std::copy( v3.begin(), v3.end(), output );
  std::pair< std::vector< int >::iterator, std::vector< int >::iterator > loca

tion;

  location = std::mismatch( v1.begin(), v1.end(), v3.begin() );
  cout << "\nThere is a mismatch between v1 and v3 at location "
     << ( location.first - v1.begin() ) << "\nwhere v1 contains "
     << *location.first << " and v3 contains " << *location.second;
  return 0;

} /* Vector v1 contains: 1 2 3 4 5 6 7 8 9 10 Vector v2 contains: 1 2 3 4 5 6 7 8 9 10 Vector v3 contains: 1 2 3 4 9 6 7 8 9 10 There is a mismatch between v1 and v3 at location 4 where v1 contains 5 and v3 contains 9

*/
       
 </source>

Generic mismatch algorithm: Find the corresponding positions in a deque and list at which unequal elements first occur

<source lang="cpp">

1. include <iostream>
2. include <cassert>
3. include <algorithm>
4. include <string>
5. include <list>
6. include <deque>
7. include <vector>

using namespace std; int main() {

 list<string> driver_list;
 vector<string> vec;
 deque<string> deq;
 driver_list.insert(driver_list.end(), "AAA");
 driver_list.insert(driver_list.end(), "BBBB");
 driver_list.insert(driver_list.end(), "CCCCC");
 deq.insert(deq.end(), "AAA");
 deq.insert(deq.end(), "DDDDDD");
 
 pair<deque<string>::iterator, list<string>::iterator> pair1 = mismatch(deq.begin(), deq.end(),driver_list.begin());
 if (pair1.first != deq.end())
   cout << "First disagreement in deq and driver_list:\n  "
        << *(pair1.first) << " and " << *(pair1.second)
        << endl;
 return 0;

} /* First disagreement in deq and driver_list:

 DDDDDD and BBBB
*/        
 </source>

Use mismatch function to find the first match

<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() {

   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

*/       
 </source>

Use mismatch function with custom function

<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() {

   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;
   /* find first position where the element of coll1 is not
    * less than the corresponding element of coll2
    */
   values = mismatch (coll1.begin(), coll1.end(),  // first range
                      coll2.begin(),               // second range
                      less_equal<int>());          // criterion
   if (values.first == coll1.end()) {
       cout << "always less-or-equal" << endl;
   }
   else {
       cout << "not less-or-equal: "
            << *values.first << " and "
            << *values.second << endl;
   }

}

/* 

coll1: 1 2 3 4 5 6 coll2: 1 2 4 8 16 3 not less-or-equal: 6 and 3

*/       
 </source>