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binary_search
Returns whether the range contains an element
Definition
The binary_search() algorithm is defined in the standard header <algorithm> and in the nonstandard backward-compatibility header <algo.h>.Interface
#include <algorithm> template < class ForwardIterator, class Type > bool binary_search( ForwardIterator first, ForwardIterator last, const Type& val ); template < class ForwardIterator, class Type, class BinaryPredicate > bool binary_search( ForwardIterator first, ForwardIterator last, const Type& val, BinaryPredicate comp );Parameters:
| Parameter | Description |
|---|---|
| first | A forward iterator addressing the position of the first element in the range to be searched |
| last | A forward iterator addressing the position one past the final element in the range to be searched |
| val | The value required to be matched by the value of the element or that must satisfy the condition with the element value specified by the binary predicate |
| comp | User-defined predicate function object that defines sense in which one element is less than another. A binary predicate takes two arguments and returns true when satisfied and false when not satisfied |
Description
Binary_search tests if there is an element in a sorted range that is equal to a specified value or that is equivalent to it in a sense specified by a binary predicate. The first version usesoperator< for comparison, and the second uses the function object comp.Example:
Example - binary_search algorithm
Problem
This program illustrates the use of the STL binary_search() algorithm
(default version) to determine whether a given integer is one of the
values in a vector of integers that are sorted in ascending order.
Workings
#include <iostream> #include <vector> #include <algorithm> using namespace std; int main() { int a[] = {1, 2, 3, 4, 5, 6, 7, 9, 10}; vector<int> v(a, a+9); cout <<"\nHere are the values in the vector:\n"; for (vector<int>::size_type i=0; i<v.size(); i++) cout <<v.at(i)<<" "; if (binary_search(v.begin(), v.end(), 3)) cout <<"\nThe value 3 was found."; else cout <<"\nThe value 3 was not found."; if (binary_search(v.begin(), v.end(), 8)) cout <<"\nThe value 8 was found."; else cout <<"\nThe value 8 was not found."; return 0; }
Solution
Output:
Here are the values in the vector:
1 2 3 4 5 6 7 9 10 The value 3 was found. The value 8 was not found.
1 2 3 4 5 6 7 9 10 The value 3 was found. The value 8 was not found.
References
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