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Difference between revisions of "cpp/algorithm/includes"

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< cpp‎ | algorithm
m (seealso par)
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{{dcl begin}}
 
{{dcl begin}}
 
{{dcl header | algorithm}}
 
{{dcl header | algorithm}}
−
{{dcl | num=1 |
+
<!-- maybe transforms a dcl into a pair of dcls, the second with parallel -->
 +
<!--- repro the original first. --->
 +
{{dcl | since= | num= 1 |1=
 +
 
 
template< class InputIt1, class InputIt2 >
 
template< class InputIt1, class InputIt2 >
 
bool includes( InputIt1 first1, InputIt1 last1,
 
bool includes( InputIt1 first1, InputIt1 last1,
 
               InputIt2 first2, InputIt2 last2 );
 
               InputIt2 first2, InputIt2 last2 );
 
}}
 
}}
−
{{dcl | num=2 |
+
{{dcl | since=c++17 | num= 2 |1=
 +
template< class ExecutionPolicy, class InputIt1, class InputIt2 >
 +
bool includes( ExecutionPolicy&& policy, InputIt1 first1, InputIt1 last1,
 +
              InputIt2 first2, InputIt2 last2 );}}
 +
<!-- maybe transforms a dcl into a pair of dcls, the second with parallel -->
 +
<!--- repro the original first. --->
 +
{{dcl | since= | num= 3 |1=
 +
 
 
template< class InputIt1, class InputIt2, class Compare >
 
template< class InputIt1, class InputIt2, class Compare >
 
bool includes( InputIt1 first1, InputIt1 last1,
 
bool includes( InputIt1 first1, InputIt1 last1,
 
               InputIt2 first2, InputIt2 last2, Compare comp );
 
               InputIt2 first2, InputIt2 last2, Compare comp );
 
}}
 
}}
 +
{{dcl | since=c++17 | num= 4 |1=
 +
template< class ExecutionPolicy, class InputIt1, class InputIt2, class Compare >
 +
bool includes( ExecutionPolicy&& policy, InputIt1 first1, InputIt1 last1,
 +
              InputIt2 first2, InputIt2 last2, Compare comp );}}
 
{{dcl end}}
 
{{dcl end}}
  
 
Returns {{c|true}} if every element from the sorted range {{tt|[first2, last2)}} is found within the sorted range {{tt|[first1, last1)}}. Also returns {{c|true}} if {{tt|[first2, last2)}} is empty.  
 
Returns {{c|true}} if every element from the sorted range {{tt|[first2, last2)}} is found within the sorted range {{tt|[first1, last1)}}. Also returns {{c|true}} if {{tt|[first2, last2)}} is empty.  
−
 
+
@1@ Both ranges must be sorted with {{c|operator<}}.
−
The first version expects both ranges to be sorted with {{c|operator<}}, the second version expects them to be sorted with the given comparison function {{tt|comp}}.
+
@3@ Both ranges must be sorted with the given comparison function {{tt|comp}}.
 +
@2,4@ Same as {{v|1,3}}, but executed according to {{tt|policy}}. These overloads do not participate in overload resolution unless {{c|std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>}} is true
  
 
===Parameters===
 
===Parameters===
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{{par | first1, last1 | the sorted range of elements to examine}}
 
{{par | first1, last1 | the sorted range of elements to examine}}
 
{{par | first2, last2 | the sorted range of elements to search for}}
 
{{par | first2, last2 | the sorted range of elements to search for}}
 +
{{par exec pol}}
 
{{par cmp ord | comp | p1=InputIt}}  
 
{{par cmp ord | comp | p1=InputIt}}  
 
{{par hreq}}
 
{{par hreq}}
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===Complexity===
 
===Complexity===
 
At most {{math|2&middot;(N<sub>1</sub>+N<sub>2</sub>-1)}} comparisons, where {{math|N<sub>1</sub>}} {{c|{{=}} std::distance(first1, last1)}} and {{math|N<sub>2</sub>}} {{c|{{=}} std::distance(first2, last2)}}.
 
At most {{math|2&middot;(N<sub>1</sub>+N<sub>2</sub>-1)}} comparisons, where {{math|N<sub>1</sub>}} {{c|{{=}} std::distance(first1, last1)}} and {{math|N<sub>2</sub>}} {{c|{{=}} std::distance(first2, last2)}}.
 +
 +
===Exceptions===
 +
{{cpp/algorithm/parallel_exceptions_reporting_behavior|singular=no}}
  
 
===Possible implementation===
 
===Possible implementation===

Revision as of 08:41, 21 March 2016

 
C++
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
Batch operations
(C++17)
Search operations
(C++11)                (C++11)(C++11)

Modifying sequence operations
Copy operations
(C++11)
(C++11)
(C++11)
Swap operations
Transformation operations
Generation operations
Removing operations
Order-changing operations
(until C++17)(C++11)
(C++20)(C++20)
Sampling operations
(C++17)

Sorting and related operations
Partitioning operations
Sorting operations
Binary search operations
(on partitioned ranges)
Set operations (on sorted ranges)
Merge operations (on sorted ranges)
Heap operations
Minimum/maximum operations
(C++11)
(C++17)
Lexicographical comparison operations
(C++20)
Permutation operations
C library
Numeric operations
Operations on uninitialized memory
 
Defined in header <algorithm>
template< class InputIt1, class InputIt2 >

bool includes( InputIt1 first1, InputIt1 last1,

               InputIt2 first2, InputIt2 last2 );
 (1)
template< class ExecutionPolicy, class InputIt1, class InputIt2 >

bool includes( ExecutionPolicy&& policy, InputIt1 first1, InputIt1 last1,

               InputIt2 first2, InputIt2 last2 );
 (2) (since C++17)
template< class InputIt1, class InputIt2, class Compare >

bool includes( InputIt1 first1, InputIt1 last1,

               InputIt2 first2, InputIt2 last2, Compare comp );
 (3)
template< class ExecutionPolicy, class InputIt1, class InputIt2, class Compare >

bool includes( ExecutionPolicy&& policy, InputIt1 first1, InputIt1 last1,

               InputIt2 first2, InputIt2 last2, Compare comp );
 (4) (since C++17)

Returns true if every element from the sorted range [first2, last2) is found within the sorted range [first1, last1). Also returns true if [first2, last2) is empty.

1) Both ranges must be sorted with operator<.
3) Both ranges must be sorted with the given comparison function comp.
2,4) Same as (1,3), but executed according to policy. These overloads do not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Contents

Parameters

first1, last1 - the sorted range of elements to examine
first2, last2 - the sorted range of elements to search for
policy - the execution policy to use. See execution policy for details.
comp - comparison function object (i.e. an object that satisfies the requirements of Compare) which returns ​true if the first argument is less than (i.e. is ordered before) the second.

The signature of the comparison function should be equivalent to the following:

bool cmp(const Type1& a, const Type2& b);

While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1& is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy(since C++11)).
The types Type1 and Type2 must be such that an object of type InputIt can be dereferenced and then implicitly converted to both of them. ​

Type requirements

Template:par req concept

Return value

true if every element from [first2, last2) is a member of [first, last).

Complexity

At most 2·(N1+N2-1) comparisons, where N1 = std::distance(first1, last1) and N2 = std::distance(first2, last2).

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.

Possible implementation

First version 
template<class InputIt1, class InputIt2>
bool includes(InputIt1 first1, InputIt1 last1,
              InputIt2 first2, InputIt2 last2)
{
    for (; first2 != last2; ++first1)
    {
        if (first1 == last1 || *first2 < *first1)
            return false;
        if ( !(*first1 < *first2) )
            ++first2;
    }
    return true;
}
Second version 
template<class InputIt1, class InputIt2>
bool includes(InputIt1 first1, InputIt1 last1,
              InputIt2 first2, InputIt2 last2, Compare comp)
{
    for (; first2 != last2; ++first1)
    {
        if (first1 == last1 || comp(*first2, *first1))
            return false;
        if (!comp(*first1, *first2))
            ++first2;
    }
    return true;
}

Example

Run this code
#include <iostream>
#include <algorithm>
#include <cctype>
#include <vector>
 
int main()
{
  std::vector<char> v1 {'a', 'b', 'c', 'f', 'h', 'x'};
  std::vector<char> v2 {'a', 'b', 'c'};
  std::vector<char> v3 {'a', 'c'};
  std::vector<char> v4 {'g'};
  std::vector<char> v5 {'a', 'c', 'g'};
 
  for (auto i : v1) std::cout << i << ' ';
  std::cout << "\nincludes:\n" << std::boolalpha;
 
  for (auto i : v2) std::cout << i << ' ';
  std::cout << ": " << std::includes(v1.begin(), v1.end(), v2.begin(), v2.end()) << '\n';
  for (auto i : v3) std::cout << i << ' ';
  std::cout << ": " << std::includes(v1.begin(), v1.end(), v3.begin(), v3.end()) << '\n';
  for (auto i : v4) std::cout << i << ' ';
  std::cout << ": " << std::includes(v1.begin(), v1.end(), v4.begin(), v4.end()) << '\n';
  for (auto i : v5) std::cout << i << ' ';
  std::cout << ": " << std::includes(v1.begin(), v1.end(), v5.begin(), v5.end()) << '\n';
 
  auto cmp_nocase = [](char a, char b) {
    return std::tolower(a) < std::tolower(b);
  };
 
  std::vector<char> v6 {'A', 'B', 'C'};
  for (auto i : v6) std::cout << i << ' ';
  std::cout << ": (case-insensitive) "
            << std::includes(v1.begin(), v1.end(), v6.begin(), v6.end(), cmp_nocase)
            << '\n';
}

Output: 

a b c f h x
includes:
a b c : true
a c : true
g : false
a c g : false
A B C : (case-insensitive) true

See also

 computes the difference between two sets
(function template) [edit]
searches for the first occurrence of a range of elements
(function template) [edit]
(parallelism TS)
 parallelized version of std::includes
(function template) [edit]
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