std::search
Defined in header
<algorithm>
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template< class ForwardIt1, class ForwardIt2 >
ForwardIt1 search( ForwardIt1 first, ForwardIt1 last, |
(1) | |
template< class ForwardIt1, class ForwardIt2, class BinaryPredicate >
ForwardIt1 search( ForwardIt1 first, ForwardIt1 last, |
(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
.
Contents |
[edit] Parameters
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. |
Type requirements | ||
-
ForwardIt1, ForwardIt2 must meet the requirements of ForwardIterator .
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[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
#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
finds the last sequence of elements in a certain range (function template) |
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returns true if one set is a subset of another (function template) |
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determines if two sets of elements are the same (function template) |
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(C++11)
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finds the first element satisfying specific criteria (function template) |
returns true if one range is lexicographically less than another (function template) |
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finds the first position where two ranges differ (function template) |
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searches for a number consecutive copies of an element in a range (function template) |
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(library fundamentals TS)
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applies a searcher to a sequence (function template) |
(parallelism TS)
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parallelized version of std::search (function template) |