[C/C++标准库]_[初级]_[集合操作]

set_difference

set_union

set_symmetric_difference

场景:

1.需要合并集合或过滤出不同集合里的元素便于操作.如一个集合里有索引值1,2.总集合里有1,2,3,4,5.需要找出3,4,5时,就需要set_symmetric_difference

#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <vector>
#include <iostream>
#include <string>

using namespace std;

//1.可重复值
//2.集合对称差
void ExampleSetSymmetricDifference()
{
	vector<int> i1;
	vector<int> i2;

//    int i1[] = {1,2,5,7};
//	int i2[] = {0,1,2,3};
//	int i2[] = {0,1,2,3,4,5,6,7};
	std::vector<int>::iterator it;
	i1.push_back(1);
	i1.push_back(2);
	i1.push_back(5);
	i1.push_back(8);

	i2.push_back(0);
	i2.push_back(1);
	i2.push_back(2);
	i2.push_back(3);
	i2.push_back(4);
	i2.push_back(5);
	i2.push_back(6);
	i2.push_back(6);
	i2.push_back(7);

    sort(i1.begin(),i1.end());
	sort(i2.begin(),i2.end());

	vector<int> res(i2.size()+i1.size());
	//对称差
	it = set_symmetric_difference(i1.begin(),i1.end(),i2.begin(),i2.end(),res.begin());

	res.resize(it-res.begin());
	size_t size = res.size();
	
	printf("size %d\n",size);
	for (it=res.begin(); it!=res.end(); ++it)
	{
		std::cout << ' ' << *it;
    }
    std::cout << std::endl;
}

//1.可重复值
//2.集合差集
void ExampleSetDifference()
{
  int first[] = {5,10,15,15,25};
  int second[] = {50,40,30,20,10};
  std::vector<int> v(10);                      // 0  0  0  0  0  0  0  0  0  0
  std::vector<int>::iterator it;

  std::sort (first,first+5);     //  5 10 15 20 25
  std::sort (second,second+5);   // 10 20 30 40 50

  //frist相对second的不同值
  it=std::set_difference (first, first+5, second, second+5, v.begin());
                                               //  5 15 25  0  0  0  0  0  0  0
  v.resize(it-v.begin());                      //  5 15 25

  std::cout << "The difference has " << (v.size()) << " elements:\n";
  for (it=v.begin(); it!=v.end(); ++it)
  {
  	   std::cout << ' ' << *it;
  }
  std::cout << std::endl;
}

//1.可重复值
//1.集合并集,共有的只出现一次
void ExampleSetUnion()
{
  int first[] = {5,10,15,15,25};
  int second[] = {50,40,30,20,10};
  std::vector<int> v(10);                      // 0  0  0  0  0  0  0  0  0  0
  std::vector<int>::iterator it;

  std::sort (first,first+5);     //  5 10 15 20 25
  std::sort (second,second+5);   // 10 20 30 40 50

  it=std::set_union (first, first+5, second, second+5, v.begin());

  v.resize(it-v.begin());
  std::cout << "The union has " << (v.size()) << " elements:\n";
  for (it=v.begin(); it!=v.end(); ++it)
  {
  		std::cout << ' ' << *it;
  }
  std::cout << std::endl;
}


int main(int argc, char *argv[])
{
	std::cout << "SetDifference" << endl;
	ExampleSetDifference();

	std::cout << "SetSymmetricDifference" << endl;
	ExampleSetSymmetricDifference();

	std::cout << "SetUnion" << endl;
	ExampleSetUnion();
	return 0;
}

输出:

SetDifference
The difference has 4 elements:
 5 15 15 25
SetSymmetricDifference
size 7
 0 3 4 6 6 7 8
SetUnion
The union has 9 elements:
 5 10 15 15 20 25 30 40 50
[Finished in 0.3s]