C++ Tutorial/STL Algorithms Binary search/binary search — различия между версиями
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Текущая версия на 10:31, 25 мая 2010
Содержание
Binary search after sorting
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
bool greater10( int value );
int main()
{
const int SIZE = 10;
int a[ SIZE ] = { 10, 2, 17, 5, 16, 8, 13, 11, 20, 7 };
vector< int > v( a, a + SIZE );
vector< int >::iterator location;
location = find( v.begin(), v.end(), 16 );
sort( v.begin(), v.end() );
if ( binary_search( v.begin(), v.end(), 13 ) )
cout << "\n\n13 was found in v";
else
cout << "\n\n13 was not found in v";
return 0;
}
bool greater10( int value ) { return value > 10; }binary_search a list
/* 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);
PRINT_ELEMENTS(coll);
// check existence of element with value 5
if (binary_search(coll.begin(), coll.end(), 5)) {
cout << "5 is present" << endl;
}
else {
cout << "5 is not present" << endl;
}
// check existence of element with value 42
if (binary_search(coll.begin(), coll.end(), 42)) {
cout << "42 is present" << endl;
}
else {
cout << "42 is not present" << endl;
}
}1 2 3 4 5 6 7 8 9 5 is present 42 is not present
Illustrating the generic binary search algorithms
#include <iostream>
#include <cassert>
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
vector<int> v(5);
bool found;
for (int i = 0; i < 5; ++i)
v[i] = i;
found = binary_search(v.begin(), v.end(), 3);
cout << found << " ";
// Try searching for a value that"s not present:
found = binary_search (v.begin(), v.end(), 9);
cout << found;
return 0;
}1 0
Use binary_search() to binary search a vector
#include <algorithm>
#include <vector>
#include <string>
#include <iostream>
using namespace std;
typedef vector <string> VECTOR_STRINGS;
int main ()
{
VECTOR_STRINGS v;
v.push_back ("A");
v.push_back ("B");
v.push_back ("C");
v.push_back ("D");
// insert a duplicate into the vector
v.push_back ("D");
for (size_t nItem = 0; nItem < v.size (); ++ nItem){
cout << "Name [" << nItem << "] = \"";
cout << v [nItem] << "\"" << endl;
}
// sort the names using std::sort
sort (v.begin (), v.end ());
for (size_t nItem = 0; nItem < v.size (); ++ nItem){
cout << "Name [" << nItem << "] = \"";
cout << v [nItem] << "\"" << endl;
}
bool bElementFound = binary_search (v.begin (), v.end (),"C");
if (bElementFound)
cout << "Result: C was found in the vector!" << endl;
else
cout << "Element not found " << endl;
return 0;
}Use binary_search to locate a value in a vector
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#include <iterator>
int main()
{
int a[ 10 ] = { 10, 2, 17, 5, 16, 8, 13, 11, 20, 7 };
std::vector< int > v( a, a + 10 ); // copy of a
std::ostream_iterator< int > output( cout, " " );
cout << "Vector v contains: ";
std::copy( v.begin(), v.end(), output ); // display output vector
// locate first occurrence of 16 in v
std::vector< int >::iterator location;
// use binary_search to locate 13 in v
if ( std::binary_search( v.begin(), v.end(), 13 ) )
cout << "\n\n13 was found in v";
else
cout << "\n\n13 was not found in v";
cout << endl;
return 0;
}Vector v contains: 10 2 17 5 16 8 13 11 20 7 13 was not found in v
