两组的交集仅由两组中都存在的元素形成。函数复制的元素始终以相同的顺序来自第一个范围。两个范围内的元素都应已订购。
例子：
Input :
5 10 15 20 25
50 40 30 20 10
Output :
The intersection has 2 elements :
10 20
1.使用“ <”比较元素：
句法 ：
Template :
OutputIterator set_intersection (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
Parameters :
first1, last1
Input iterators to the initial and final positions of the first
sorted sequence. The range used is [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
Input iterators to the initial and final positions of the second
sorted sequence. The range used is [first2, last2).
result
Output iterator to the initial position of the range where the
resulting sequence is stored.
The pointed type shall support being assigned the value of an
element from the first range.
Return Type :
An iterator to the end of the constructed range.
// CPP program to illustrate
// std :: set_intersection
#include
int main()
{
int first[] = { 5, 10, 15, 20, 25 };
int second[] = { 50, 40, 30, 20, 10 };
int n = sizeof(first) / sizeof(first[0]);
std::vector v1(5);
std::vector v2(5);
std::vector::iterator it, ls;
std::sort(first, first + 5);
std::sort(second, second + 5);
// Print elements
std::cout << "First array :";
for (int i = 0; i < n; i++)
std::cout << " " << first[i];
std::cout << "\n";
// Print elements
std::cout << "Second array :";
for (int i = 0; i < n; i++)
std::cout << " " << second[i];
std::cout << "\n\n";
// std :: set_intersection
ls = std::set_intersection(first, first + 5, second, second + 5, v1.begin());
std::cout << "The intersection has " << (ls - v1.begin()) << " elements:";
for (it = v1.begin(); it != ls; ++it)
std::cout << ' ' << *it;
std::cout << "\n";
return 0;
}
输出：
First array : 5 10 15 20 25
Second array : 10 20 30 40 50
The intersection has 2 elements: 10 20
2.通过使用预定义函数进行比较：
Synatax：
Template :
OutputIterator set_intersection (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
Parameters :
first1, last1, first2, last2, result are same as mentioned above.
comp
Binary function that accepts two arguments of the types pointed
by the input iterators, and returns a value convertible to bool.
The function shall not modify any of its arguments.
This can either be a function pointer or a function object.
It follows the strict weak ordering to order the elements.
Return Type :
An iterator to the end of the constructed range.
// CPP program to illustrate
// std :: set_intersection
#include
bool comp(int a, int b)
{
return a < b;
}
int main()
{
int first[] = { 5, 10, 15, 20, 25 };
int second[] = { 50, 40, 30, 20, 10 };
int n = sizeof(first) / sizeof(first[0]);
std::vector v1(5);
std::vector v2(5);
std::vector::iterator it, ls;
std::sort(first, first + 5);
std::sort(second, second + 5);
// Print elements
std::cout << "First array :";
for (int i = 0; i < n; i++)
std::cout << " " << first[i];
std::cout << "\n";
// Print elements
std::cout << "Second array :";
for (int i = 0; i < n; i++)
std::cout << " " << second[i];
std::cout << "\n\n";
// std :: set_intersection
ls = std::set_intersection(first, first + 5, second, second + 5, v1.begin(), comp);
std::cout << "The intersection has " << (ls - v1.begin()) << " elements:";
for (it = v1.begin(); it != ls; ++it)
std::cout << ' ' << *it;
std::cout << "\n";
return 0;
}
输出：
First array : 5 10 15 20 25
Second array : 10 20 30 40 50
The intersection has 2 elements: 10 20
可能的应用：用于查找仅在两个集合中都存在的元素。
1.可用于查找两个班级中存在的学生列表。
// CPP program to demonstrate use of
// std :: set_intersection
#include
#include
#include
#include
using namespace std;
// Driver code
int main()
{
string first[] = { "Sachin", "Rakesh", "Sandeep", "Serena" };
string second[] = { "Vaibhav", "Sandeep", "Rakesh", "Neha" };
int n = sizeof(first) / sizeof(first[0]);
// Print students of first list
cout << "Students in first class :";
for (int i = 0; i < n; i++)
cout << " " << first[i];
cout << "\n";
// Print students of second list
cout << "Students in second class :";
for (int i = 0; i < n; i++)
cout << " " << second[i];
cout << "\n\n";
vector v(10);
vector::iterator it, st;
// Sorting both the list
sort(first, first + n);
sort(second, second + n);
// Using default operator<
it = set_intersection(first, first + n, second, second + n, v.begin());
cout << "Students attending both the classes only are :\n";
for (st = v.begin(); st != it; ++st)
cout << ' ' << *st;
cout << '\n';
return 0;
}
输出 ：
Students in first class : Sachin Rakesh Sandeep Serena
Students in second class : Vaibhav Sandeep Rakesh Neha
Students attending both classes only are :
Rakesh Sandeep
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