`std::set_intersection` 用于计算两个已排序范围的交集。它将交集的结果写入到指定的输出迭代器中。
`std::set_union` 用于计算两个已排序范围的并集。它将并集的结果写入到指定的输出迭代器中。
`std::set_difference` 用于计算两个已排序范围的差集。它将差集的结果写入到指定的输出迭代器中。差集是指在第一个范围中存在但在第二个范围中不存在的元素。
`std::set_symmetric_difference` 用于计算两个已排序范围的对称差集。对称差集是指在两个范围中存在但不在两个范围的交集中存在的元素。它将对称差集的结果写入到指定的输出迭代器中。
即:并集减差集:set_union - set_intersection
这几个函数默认使用 < 运算符,除非自定义比较函数。
std::set_intersection
用于计算两个已排序范围的交集。它将交集的结果写入到指定的输出迭代器中。
Defined in header | ||
template< class InputIt1, class InputIt2, class OutputIt > OutputIt set_intersection( InputIt1 first1, InputIt1 last1, | (1) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class ForwardIt3 > | (2) | (since C++17) |
template< class InputIt1, class InputIt2, class OutputIt, class Compare > | (3) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, | (4) | (since C++17) |
Constructs a sorted range beginning at d_first consisting of elements that are found in both sorted ranges [
first1,
last1)
and [
first2,
last2)
.
If [
first1,
last1)
contains m elements that are equivalent to each other and [
first2,
last2)
contains n elements that are equivalent to them, the first std::min(m, n) elements will be copied from [
first1,
last1)
to the output range, preserving order.
1) If [
first1,
last1)
or [
first2,
last2)
is not sorted with respect to operator<(until C++20)std::less{}(since C++20), the behavior is undefined.
3) If [
first1,
last1)
or [
first2,
last2)
is not sorted with respect to comp, the behavior is undefined.
2,4) Same as (1,3), but executed according to policy.
If the output range overlaps with [
first1,
last1)
or [
first2,
last2)
, the behavior is undefined.
### 参数
- `first1`, `last1`: 第一个已排序范围的起始和结束迭代器。
- `first2`, `last2`: 第二个已排序范围的起始和结束迭代器。
- `d_first`: 输出范围的起始迭代器。
- `comp`: 二元谓词,用于比较元素。
### 返回值
返回一个迭代器,指向输出范围的末尾,即最后一个写入元素之后的位置。
### 示例
以下是一个简单的例子,演示如何使用 `std::set_intersection`:
#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
int main()
{
std::vector<int> v1{7, 2, 3, 4, 5, 6, 7, 8};
std::vector<int> v2{5, 7, 9, 7};
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 << ' ';
std::cout << '\n';
}
Output:
5 7 7
### 自定义比较函数
#include <iostream>
#include <vector>
#include <algorithm>
bool compare(int a, int b) {
return a < b;
}
int main() {
std::vector<int> vec1 = {1, 2, 3, 4, 5};
std::vector<int> vec2 = {3, 4, 5, 6, 7};
std::vector<int> result;
std::set_intersection(vec1.begin(), vec1.end(), vec2.begin(), vec2.end(), std::back_inserter(result), compare);
std::cout << "Intersection of vec1 and vec2: ";
for (int n : result) {
std::cout << n << " ";
}
std::cout << std::endl;
return 0;
}
在这个例子中,`std::set_intersection` 使用 `compare` 函数来比较元素。
std::set_union
用于计算两个已排序范围的并集。它将并集的结果写入到指定的输出迭代器中。
### 语法
Defined in header | ||
template< class InputIt1, class InputIt2, class OutputIt > OutputIt set_union( InputIt1 first1, InputIt1 last1, | (1) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class ForwardIt3 > | (2) | (since C++17) |
template< class InputIt1, class InputIt2, class OutputIt, class Compare > | (3) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, | (4) | (since C++17) |
Constructs a sorted union beginning at d_first consisting of the set of elements present in one or both sorted ranges [
first1,
last1)
and [
first2,
last2)
.
If [
first1,
last1)
contains m elements that are equivalent to each other and [
first2,
last2)
contains n elements that are equivalent to them, then all m elements will be copied from [
first1,
last1)
to the output range, preserving order, and then the final std::max(n - m, 0) elements will be copied from [
first2,
last2)
to the output range, also preserving order.
1) If [
first1,
last1)
or [
first2,
last2)
is not sorted with respect to operator<(until C++20)std::less{}(since C++20), the behavior is undefined.
3) If [
first1,
last1)
or [
first2,
last2)
is not sorted with respect to comp, the behavior is undefined.
2,4) Same as (1,3), but executed according to policy.
These overloads participate in overload resolution only if all following conditions are satisfied:
If the output range overlaps with [
first1,
last1)
or [
first2,
last2)
, the behavior is undefined.
### 参数
- `first1`, `last1`: 第一个已排序范围的起始和结束迭代器。
- `first2`, `last2`: 第二个已排序范围的起始和结束迭代器。
- `d_first`: 输出范围的起始迭代器。
- `comp`: 二元谓词,用于比较元素。
### 返回值
返回一个迭代器,指向输出范围的末尾,即最后一个写入元素之后的位置。
### 示例
以下是一个简单的例子,演示如何使用 `std::set_union`:
#include <iostream>
#include <vector>
#include <algorithm>
int main() {
std::vector<int> vec1 = {1, 2, 3, 4, 5};
std::vector<int> vec2 = {3, 4, 5, 6, 7};
std::vector<int> result;
std::set_union(vec1.begin(), vec1.end(), vec2.begin(), vec2.end(), std::back_inserter(result));
std::cout << "Union of vec1 and vec2: ";
for (int n : result) {
std::cout << n << " ";
}
std::cout << std::endl;
return 0;
}
output:
Union of vec1 and vec2: 1 2 3 4 5 6 7
### 自定义比较函数
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
struct MyStruct {
int key;
int value;
};
// 自定义比较函数,比较 MyStruct 的 value 成员的绝对值
bool compare(const MyStruct& a, const MyStruct& b) {
return std::abs(a.value) < std::abs(b.value);
}
int main() {
std::vector<MyStruct> vec1 = {{1, 10}, {2, -20}, {3, 30}, {4, -40}, {5, 50}};
std::vector<MyStruct> vec2 = {{3, -300}, {4, 400}, {5, -500}, {6, 600}, {7, -700}};
std::vector<MyStruct> result;
std::set_union(vec1.begin(), vec1.end(), vec2.begin(), vec2.end(), std::back_inserter(result), compare);
std::cout << "Union of vec1 and vec2: ";
for (const auto& elem : result) {
std::cout << "{" << elem.key << ", " << elem.value << "} ";
}
std::cout << std::endl;
return 0;
}
在这个例子中,`std::set_union` 使用 `compare` 函数来比较元素。
std::set_difference
用于计算两个已排序范围的差集。它将差集的结果写入到指定的输出迭代器中。差集是指在第一个范围中存在但在第二个范围中不存在的元素。
### 语法
Defined in header | ||
template< class InputIt1, class InputIt2, class OutputIt > OutputIt set_difference( InputIt1 first1, InputIt1 last1, | (1) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class ForwardIt3 > | (2) | (since C++17) |
template< class InputIt1, class InputIt2, class OutputIt, class Compare > | (3) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, | (4) | (since C++17) |
Copies the elements from the sorted range [
first1,
last1)
which are not found in the sorted range [
first2,
last2)
to the range beginning at d_first. The output range is also sorted.
If [
first1,
last1)
contains m elements that are equivalent to each other and [
first2,
last2)
contains n elements that are equivalent to them, the final std::max(m - n, 0) elements will be copied from [
first1,
last1)
to the output range, preserving order.
1) If [
first1,
last1)
or [
first2,
last2)
is not sorted with respect to operator<(until C++20)std::less{}(since C++20), the behavior is undefined.
3) If [
first1,
last1)
or [
first2,
last2)
is not sorted with respect to comp, the behavior is undefined.
2,4) Same as (1,3), but executed according to policy.
If the output range overlaps with [
first1,
last1)
or [
first2,
last2)
, the behavior is undefined.
### 参数
- `first1`, `last1`: 第一个已排序范围的起始和结束迭代器。
- `first2`, `last2`: 第二个已排序范围的起始和结束迭代器。
- `d_first`: 输出范围的起始迭代器。
- `comp`: 二元谓词,用于比较元素。
### 返回值
返回一个迭代器,指向输出范围的末尾,即最后一个写入元素之后的位置。
### 示例
以下是一个简单的例子,演示如何使用 `std::set_difference`:
//在vec1中不在vec2中的元素
#include <iostream>
#include <vector>
#include <algorithm>
int main() {
std::vector<int> vec1 = {1, 3, 2, 4, 5};
std::vector<int> vec2 = {3, 5, 4, 6, 7};
std::vector<int> result;
std::sort(vec1.begin(), vec1.end());
std::sort(vec2.begin(), vec2.end());
std::set_difference(vec1.begin(), vec1.end(), vec2.begin(), vec2.end(), std::back_inserter(result));
std::cout << "Difference of vec1 and vec2: ";
for (int n : result) {
std::cout << n << " ";
}
std::cout << std::endl;
return 0;
}
输出:
Difference of vec1 and vec2: 1 2
### 自定义比较函数
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
struct MyStruct {
int key;
int value;
};
// 自定义比较函数,比较 MyStruct 的 value 成员的绝对值
bool compare(const MyStruct& a, const MyStruct& b) {
return std::abs(a.value) < std::abs(b.value);
}
int main() {
std::vector<MyStruct> vec1 = {{1, 10}, {2, -20}, {3, 30}, {4, -40}, {5, 50}, {9, -90}};
std::vector<MyStruct> vec2 = {{3, -300}, {4, 400}, {5, -500}, {6, 600}, {7, -700}, {10, 1000}};
std::vector<MyStruct> result;
std::set_difference(vec1.begin(), vec1.end(), vec2.begin(), vec2.end(), std::back_inserter(result), compare);
std::cout << "Difference of vec1 and vec2: ";
for (const auto& elem : result) {
std::cout << "{" << elem.key << ", " << elem.value << "} ";
}
std::cout << std::endl;
return 0;
}
在这个例子中,`std::set_difference` 使用 `compare` 函数来比较元素。
std::set_symmetric_difference
用于计算两个已排序范围的对称差集。对称差集是指在两个范围中存在但不在两个范围的交集中存在的元素。它将对称差集的结果写入到指定的输出迭代器中。
即:并集减差集
### 语法
Defined in header | ||
template< class InputIt1, class InputIt2, class OutputIt > OutputIt set_symmetric_difference | (1) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class ForwardIt3 > | (2) | (since C++17) |
template< class InputIt1, class InputIt2, class OutputIt, class Compare > | (3) | (constexpr since C++20) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, |
### 参数
- `first1`, `last1`: 第一个已排序范围的起始和结束迭代器。
- `first2`, `last2`: 第二个已排序范围的起始和结束迭代器。
- `d_first`: 输出范围的起始迭代器。
- `comp`: 二元谓词,用于比较元素。
### 返回值
返回一个迭代器,指向输出范围的末尾,即最后一个写入元素之后的位置。
### 示例
#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
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_symDifference;
std::set_symmetric_difference(v1.begin(), v1.end(), v2.begin(), v2.end(),
std::back_inserter(v_symDifference));
for (int n : v_symDifference)
std::cout << n << ' ';
std::cout << '\n';
}
Output:
1 2 3 4 6 8 9 10
### 自定义比较函数
#include <iostream>
#include <vector>
#include <algorithm>
struct MyStruct {
int key;
int value;
};
bool compare(const MyStruct& a, const MyStruct& b) {
return a.key < b.key;
}
int main() {
std::vector<MyStruct> vec1 = {{1, 10}, {2, 20}, {3, 30}, {4, 40}, {5, 50}};
std::vector<MyStruct> vec2 = {{3, 300}, {4, 400}, {5, 500}, {6, 600}, {7, 700}};
std::vector<MyStruct> result;
std::set_symmetric_difference(vec1.begin(), vec1.end(), vec2.begin(), vec2.end(), std::back_inserter(result), compare);
std::cout << "Symmetric difference of vec1 and vec2: ";
for (const auto& elem : result) {
std::cout << "{" << elem.key << ", " << elem.value << "} ";
}
std::cout << std::endl;
return 0;
}
output:
Symmetric difference of vec1 and vec2: {1, 10} {2, 20} {6, 600} {7, 700}
在这个例子中,`std::set_symmetric_difference` 使用 `compare` 函数来比较元素。