chapter11-22.cpp

C++STL程序员开发指南

//文件名:CHAPTER11-22.cpp
#include <list>
#include <vector>
#include <algorithm>
#include <iostream>
// Return whether modulus of elem1 is less than modulus of elem2
bool mod_lesser ( int elem1, int elem2 )
{
   if (elem1 < 0)      elem1 = - elem1;
   if (elem2 < 0)      elem2 = - elem2;
   return elem1 < elem2;
}
int main( )
{
   using namespace std;
   list <int> L;
   list <int>::iterator Iter;
   bool b1, b2;
   L.push_back( 50 );
   L.push_back( 10 );
   L.push_back( 30 );
   L.push_back( 20 );
   L.push_back( 25 );
   L.push_back( 5 );
   L.sort( );
   cout << "L = ( " ;
   for ( Iter = L.begin( ) ; Iter != L.end( ) ; Iter++ )
      cout << *Iter << " ";
   cout << ")" << endl;
   b1 = binary_search( L.begin( ), L.end( ), 10 );
   if  ( b1 )
      cout << "There is an element in list L with a value equal to 10."<< endl;
   else
      cout << "There is no element in list L with a value equal to 10."<< endl;
   // a binary_search under the binary predicate greater
   L.sort ( greater<int> ( ) );
   b2 = binary_search( L.begin( ), L.end( ), 10 , greater<int> ( ) );
   if  ( b2 )
      cout << "There is an element in list L with a value equivalent to 10 "
           << "under greater than." << endl;
   else
      cout << "No element in list L with a value equivalent to 10 "<< "under greater than." << endl;
   // a binary_search under the user-defined binary predicate mod_lesser
   vector <int> v1;
   vector <int>::iterator Iter1;
   int i;
   for ( i = -2 ; i <= 4 ; i++ )
   {      v1.push_back( i );   }
   sort ( v1.begin ( ) , v1.end ( ) , mod_lesser );
   cout << "Ordered under mod_lesser, vector v1 = ( " ;
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
      cout << *Iter1 << " ";
   cout << ")" << endl;
   bool b3 = binary_search( v1.begin( ), v1.end( ), -3 , mod_lesser );
   if ( b3 )
      cout << "There is an element with a value equivalent to -3 "<< "under mod_lesser." << endl;
   else
      cout << "There is not an element with a value equivalent to -3 "
<< "under mod_lesser." << endl;
}