C++/STL Algorithms Binary search/binary search
binary_search a list
<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. */
- 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
*/ </source>
Illustrating the generic binary search algorithms
<source lang="cpp">
- 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
*/ </source>
Use binary_search to locate a value in a vector
<source lang="cpp">
- 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
*/ </source>