std::search

Defined in header `<algorithm>`
template< class ForwardIt1, class ForwardIt2 > ForwardIt1 search( ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last );	(1)
template< class ForwardIt1, class ForwardIt2, class BinaryPredicate > ForwardIt1 search( ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p );	(2)

Searches for the first occurrence of the subsequence of elements [s_first, s_last) in the range [first, last - (s_last - s_first)). The first version uses operator== to compare the elements, the second version uses the given binary predicate p.

first, last	-	the range of elements to examine
s_first, s_last	-	the range of elements to search for
p	-	binary predicate which returns true if the elements should be treated as equal. The signature of the predicate function should be equivalent to the following: bool pred(const Type1 &a, const Type2 &b); The signature does not need to have const &, but the function must not modify the objects passed to it. The types Type1 and Type2 must be such that objects of types ForwardIt1 and ForwardIt2 can be dereferenced and then implicitly converted to Type1 and Type2 respectively.
Type requirements
- `ForwardIt1, ForwardIt2` must meet the requirements of `ForwardIterator`.

[edit] Return value

Iterator to the beginning of first subsequence [s_first, s_last) in the range [first, last - (s_last - s_first)). If no such subsequence is found, last is returned.
If [s_first, s_last) is empty, first is returned. (since C++11)

[edit] Complexity

At most S*N comparisons where S = std::distance(s_first, s_last) and N = std::distance(first, last).

[edit] Possible implementation

First version

template<class ForwardIt1, class ForwardIt2>
ForwardIt1 search(ForwardIt1 first, ForwardIt1 last,
                        ForwardIt2 s_first, ForwardIt2 s_last)
{
    for (; ; ++first) {
        ForwardIt1 it = first;
        for (ForwardIt2 s_it = s_first; ; ++it, ++s_it) {
            if (s_it == s_last) {
                return first;
            }
            if (it == last) {
                return last;
            }
            if (!(*it == *s_it)) {
                break;
            }
        }
    }
}

Second version

template<class ForwardIt1, class ForwardIt2, class BinaryPredicate>
ForwardIt1 search(ForwardIt1 first, ForwardIt1 last,
                        ForwardIt2 s_first, ForwardIt2 s_last, 
                        BinaryPredicate p)
{
    for (; ; ++first) {
        ForwardIt1 it = first;
        for (ForwardIt2 s_it = s_first; ; ++it, ++s_it) {
            if (s_it == s_last) {
                return first;
            }
            if (it == last) {
                return last;
            }
            if (!p(*it, *s_it)) {
                break;
            }
        }
    }
}

[edit] Example

Run this code

#include <string>
#include <algorithm>
#include <iostream>
#include <vector>
 
template<typename Container>
bool in_quote(const Container& cont, const std::string& s)
{
    return std::search(cont.begin(), cont.end(), s.begin(), s.end()) != cont.end();
}
 
int main()
{
    std::string str = "why waste time learning, when ignorance is instantaneous?";
    // str.find() can be used as well
    std::cout << std::boolalpha << in_quote(str, "learning") << '\n'
                                << in_quote(str, "lemming")  << '\n';
 
    std::vector<char> vec(str.begin(), str.end());
    std::cout << std::boolalpha << in_quote(vec, "learning") << '\n'
                                << in_quote(vec, "lemming")  << '\n';
}

Output:

true
false
true
false

[edit] See also

find_end	finds the last sequence of elements in a certain range (function template)
includes	returns true if one set is a subset of another (function template)
equal	determines if two sets of elements are the same (function template)
findfind_iffind_if_not (C++11)	finds the first element satisfying specific criteria (function template)
lexicographical_compare	returns true if one range is lexicographically less than another (function template)
mismatch	finds the first position where two ranges differ (function template)
search_n	searches for a number consecutive copies of an element in a range (function template)
std::experimental::search (library fundamentals TS)	applies a searcher to a sequence (function template)
std::experimental::parallel::search (parallelism TS)	parallelized version of `std::search` (function template)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Technical Specifications