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

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Check for mismatch between two vectors

#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#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 > location;
   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

Demonstrates standard library functions equal, mismatch, lexicographical_compare.

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
   const int SIZE = 10;
   int a1[ SIZE ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
   int a2[ SIZE ] = { 1, 2, 3, 4, 1000, 6, 7, 8, 9, 10 };
   vector< int > v1( a1, a1 + SIZE ),
                 v2( a1, a1 + SIZE ),
                 v3( a2, a2 + SIZE );
   bool result = equal( v1.begin(), v1.end(), v2.begin() );
   cout << "\n\nVector v1 " << ( result ? "is" : "is not" ) 
        << " equal to vector v2.\n";
   result = equal( v1.begin(), v1.end(), v3.begin() );
   cout << "Vector v1 " << ( result ? "is" : "is not" ) 
        << " equal to vector v3.\n";
   pair< vector< int >::iterator,
         vector< int >::iterator > location;
   location = 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 
        << "\n\n";
   char c1[ SIZE ] = "HELLO", c2[ SIZE ] = "BYE BYE";
   result = lexicographical_compare( c1, c1 + SIZE, c2, c2 + SIZE );
   cout << c1 
        << ( result ? " is less than " : " is greater than " )
        << c2;
   cout << endl;
   return 0;
}

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

#include <iostream>
#include <cassert>
#include <algorithm>
#include <string>
#include <list>
#include <deque>
#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

Use mismatch function to find the first match

/* 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

Use mismatch function with custom function

/* 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;
    /* 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