std::find_first_of - cppreference.com (original) (raw)

Searches the range [first, last) for any of the elements in the range [s_first, s_last).

1. Elements are compared using operator==.

2. Elements are compared using the given binary predicate p.

2,4) Same as (1,3), but executed according to policy.

These overloads participate in overload resolution only if all following conditions are satisfied:

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Exceptions
• 5 Possible implementation
• 6 Example
• 7 Defect reports
• 8 See also

[edit] Parameters

[edit] Return value

Iterator to the first element in the range [first, last) that is equal to an element from the range [s_first, s_last).

If [s_first, s_last) is empty or if no such element is found, last is returned.

[edit] Complexity

Given \(\scriptsize N\)N as std::distance(first, last) and \(\scriptsize S\)S as std::distance(s_first, s_last):

1,2) At most \(\scriptsize N\cdot S\)N·S comparisons using operator==.

3,4) At most \(\scriptsize N\cdot S\)N·S applications of the predicate p.

[edit] Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

[edit] Possible implementation

[edit] Example

The following code searches for any of specified integers in a vector of integers:

#include #include #include   auto print_sequence = [](const auto id, const auto& seq, int pos = -1) { std::cout << id << "{ "; for (int i{}; auto const& e : seq) { const bool mark{i == pos}; std::cout << (i++ ? ", " : ""); std::cout << (mark ? "[ " : "") << e << (mark ? " ]" : ""); } std::cout << " }\n"; };   int main() { const std::vector v{0, 2, 3, 25, 5}; const auto t1 = {19, 10, 3, 4}; const auto t2 = {1, 6, 7, 9};   auto find_any_of = [](const auto& v, const auto& t) { const auto result = std::find_first_of(v.begin(), v.end(), t.begin(), t.end()); if (result == v.end()) { std::cout << "No elements of v are equal to any element of "; print_sequence("t = ", t); print_sequence("v = ", v); } else { const auto pos = std::distance(v.begin(), result); std::cout << "Found a match (" << *result << ") at position " << pos; print_sequence(", where t = ", t); print_sequence("v = ", v, pos); } };   find_any_of(v, t1); find_any_of(v, t2); }

Output:

Found a match (3) at position 2, where t = { 19, 10, 3, 4 } v = { 0, 2, [ 3 ], 25, 5 } No elements of v are equal to any element of t = { 1, 6, 7, 9 } v = { 0, 2, 3, 25, 5 }

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also