std::set_intersection

来自cppreference.com

 
 
算法库
功能
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Functions
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修改序列操作
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Non-modifying sequence operations
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all_of
any_of
none_of
(C++11)
(C++11)
(C++11)
for_each
count
count_if
mismatch
equal
修改序列操作
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Modifying sequence operations
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分区操作
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Partitioning operations
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is_partitioned(C++11)
partition
partition_copy(C++11)
排序操作(排序的区间)
Original:
Sorting operations (on sorted ranges)
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is_sorted(C++11)
is_sorted_until(C++11)
sort
二进制搜索操作(排序的区间)
Original:
Binary search operations (on sorted ranges)
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设置操作(排序的区间)
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Set operations (on sorted ranges)
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堆的操作
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Heap operations
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最小/最大操作
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Minimum/maximum operations
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数字操作
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Numeric operations
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C库
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C library
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Defined in header <algorithm>
template< class InputIt1, class InputIt2, class OutputIt >

OutputIt set_intersection( InputIt1 first1, InputIt1 last1,
                           InputIt2 first2, InputIt2 last2,

                           OutputIt d_first );
(1)
template< class InputIt1, class InputIt2,

          class OutputIt, class Compare >
OutputIt set_intersection( InputIt1 first1, InputIt1 last1,
                           InputIt2 first2, InputIt2 last2,

                           OutputIt d_first, Compare comp );
(2)
构造一个排序的范围开始,d_first中发现的两个排序范围的元素组成的[first1, last1)[first2, last2)。预计两个输入范围进行排序与​​operator<的第一个版本,第二个版本需要进行排序的比较函数comp。如果一些元素被发现m[first1, last1)n[first2, last2)的时候,第一std::min(m, n)元素将被复制到目的范围从第一个范围。等同元件的顺序被保留。由此获得的范围不能重叠的输入范围.
Original:
Constructs a sorted range beginning at d_first consisting of elements that are found in both sorted ranges [first1, last1) and [first2, last2). The first version expects both input ranges to be sorted with operator<, the second version expects them to be sorted with the given comparison function comp. If some element is found m times in [first1, last1) and n times in [first2, last2), the first std::min(m, n) elements will be copied from the first range to the destination range. The order of equivalent elements is preserved. The resulting range cannot overlap with either of the input ranges.
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目录

[编辑] 参数

first1, last1 -
检查的元素
Original:
the first range of elements to examine
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first2, last2 -
第二次检查的元素
Original:
the second range of elements to examine
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comp - comparison function which returns ​true if the first argument is less than the second.

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

bool cmp(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 InputIt1 and InputIt2 can be dereferenced and then implicitly converted to  Type1 and  Type2 respectively. ​

Type requirements
-
InputIt1 must meet the requirements of InputIterator.
-
InputIt2 must meet the requirements of InputIterator.
-
OutputIt must meet the requirements of OutputIterator.

[编辑] 返回值

过去的结尾的Iterator构建范围.
Original:
Iterator past the end of the constructed range.
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[编辑] 复杂性

2·(N1+N2-1)比较,其中N1= std::distance(first1, last1)N2= std::distance(first2, last2).
Original:
At most 2·(N1+N2-1) comparisons, where N1 = std::distance(first1, last1) and N2 = std::distance(first2, last2).
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[编辑] 可能的实现

First version
template<class InputIt1, class InputIt2, class OutputIt>
OutputIt set_intersection(InputIt1 first1, InputIt1 last1,
                          InputIt2 first2, InputIt2 last2,
                          OutputIt d_first)
{
    while (first1 != last1 && first2 != last2) {
        if (*first1 < *first2) {
            ++first1;
        } else  {
            if (!(*first2 < *first1)) {
                *d_first++ = *first1++;
            }
            ++first2;
        }
    }
    return d_first;
}
Second version
template<class InputIt1, class InputIt2,
         class OutputIt, class Compare>
OutputIt set_intersection(InputIt1 first1, InputIt1 last1,
                          InputIt2 first2, InputIt2 last2,
                          OutputIt d_first, Compare comp)
{
    while (first1 != last1 && first2 != last2) {
        if (comp(*first1, *first2)) {
            ++first1;
        } else {
            if (!comp(*first2, *first1)) {
                *d_first++ = *first1++;
            }
            ++first2;
        }
    }
    return d_first;
}


[编辑] 为例

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
int main()
{
    std::vector<int> v1{1,2,3,4,5,6,7,8};
    std::vector<int> v2{        5,  7,  9,10};
    std::sort(v1.begin(), v1.end());
    std::sort(v2.begin(), v2.end());
 
    std::vector<int> v_intersection;
 
    std::set_intersection(v1.begin(), v1.end(),
                          v2.begin(), v2.end(),
                          std::back_inserter(v_intersection));
    for(int n : v_intersection)
        std::cout << n << ' ';
}

Output:

5 7

[编辑] 另请参阅

computes the union of two sets
(函数模板) [edit]