如何在C ++中找到两个std :: set的交集? [英] how to find the intersection of two std::set in C++?

问题描述

我一直试图在C ++中找到两个std :: set之间的交集，但我一直遇到错误.

I have been trying to find the intersection between two std::set in C++, but I keep getting an error.

为此我创建了一个小样本测试

I created a small sample test for this

#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
using namespace std;

int main() {
  set<int> s1;
  set<int> s2;

  s1.insert(1);
  s1.insert(2);
  s1.insert(3);
  s1.insert(4);

  s2.insert(1);
  s2.insert(6);
  s2.insert(3);
  s2.insert(0);

  set_intersection(s1.begin(),s1.end(),s2.begin(),s2.end());
  return 0;
}

后一个程序不会生成任何输出，但是我希望具有以下值的新集(将其称为s3):

The latter program does not generate any output, but I expect to have a new set (let's call it s3) with the following values:

s3 = [ 1 , 3 ]

相反，我得到了错误:

test.cpp: In function ‘int main()’:
test.cpp:19: error: no matching function for call to ‘set_intersection(std::_Rb_tree_const_iterator<int>, std::_Rb_tree_const_iterator<int>, std::_Rb_tree_const_iterator<int>, std::_Rb_tree_const_iterator<int>)’

我从此错误中了解到的是，set_intersection中没有定义接受Rb_tree_const_iterator<int>作为参数.

What I understand out of this error, is that there's no definition in set_intersection that accepts Rb_tree_const_iterator<int> as parameter.

此外，我想std::set.begin()方法返回此类对象

Furthermore, I suppose the std::set.begin() method returns an object of such type,

是否有更好的方法在C ++中找到两个std::set的交集?最好是内置功能?

is there a better way to find the intersection of two std::set in C++? Preferably a built-in function?

非常感谢！

推荐答案

您尚未为 set_intersection

template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator set_intersection ( InputIterator1 first1, InputIterator1 last1,
                                InputIterator2 first2, InputIterator2 last2,
                                OutputIterator result );

通过类似

...;
set<int> intersect;
set_intersection(s1.begin(),s1.end(),s2.begin(),s2.end(),
                  std::inserter(intersect,intersect.begin()));

您需要一个std::insert迭代器，因为该集合截至目前为空.我们不能使用back_或front_inserter，因为set不支持这些操作.

You need a std::insert iterator since the set is as of now empty. We cannot use back_ or front_inserter since set doesnt support those operations.

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