function template
<algorithm>
std::search equality (1)template <class ForwardIterator1, class ForwardIterator2> ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2);predicate (2)
template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate> ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred);
Search range for subsequence
Searches the range[first1,last1) for the first occurrence of the sequence defined by [first2,last2), and returns an iterator to its first element, or last1 if no occurrences are found.
The elements in both ranges are compared sequentially using operator== (or pred, in version (2)): A subsequence of [first1,last1) is considered a match only when this is true for all the elements of [first2,last2).
This function returns the first of such occurrences. For an algorithm that returns the last instead, see find_end.
The behavior of this function template is equivalent to:
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template<class ForwardIterator1, class ForwardIterator2>
ForwardIterator1 search ( ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2)
{
if (first2==last2) return first1; // specified in C++11
while (first1!=last1)
{
ForwardIterator1 it1 = first1;
ForwardIterator2 it2 = first2;
while (*it1==*it2) { // or: while (pred(*it1,*it2)) for version 2
++it1; ++it2;
if (it2==last2) return first1;
if (it1==last1) return last1;
}
++first1;
}
return last1;
}[first1,last1), which contains all the elements between first1 and last1, including the element pointed by first1 but not the element pointed by last1.
[first2,last2).
operator== (with the elements of the first range as left-hand side operands, and those of the second as right-hand side operands).
bool. The returned value indicates whether the elements are considered to match in the context of this function.
[first2,last2) in [first1,last1).
If [first2,last2) is an empty range, the result is unspecified.
If [first2,last2) is an empty range, the function returns first1.
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// search algorithm example
#include <iostream> // std::cout
#include <algorithm> // std::search
#include <vector> // std::vector
bool mypredicate (int i, int j) {
return (i==j);
}
int main () {
std::vector<int> haystack;
// set some values: haystack: 10 20 30 40 50 60 70 80 90
for (int i=1; i<10; i++) haystack.push_back(i*10);
// using default comparison:
int needle1[] = {40,50,60,70};
std::vector<int>::iterator it;
it = std::search (haystack.begin(), haystack.end(), needle1, needle1+4);
if (it!=haystack.end())
std::cout << "needle1 found at position " << (it-haystack.begin()) << '\n';
else
std::cout << "needle1 not found\n";
// using predicate comparison:
int needle2[] = {20,30,50};
it = std::search (haystack.begin(), haystack.end(), needle2, needle2+3, mypredicate);
if (it!=haystack.end())
std::cout << "needle2 found at position " << (it-haystack.begin()) << '\n';
else
std::cout << "needle2 not found\n";
return 0;
}needle1 found at position 3 needle2 not found
count1*count2 (where countX is the distance between firstX and lastX): Compares elements until a matching subsequence is found.
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