set_union的几个例子

获得两个集合的并集。两个输入序列须保证已排好序。

数组用的时候

// set_union example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;  

int main () {
  int first[] = {5,10,15,20,25};
  int second[] = {50,40,30,20,10};
  vector<int> v(10);                           // 0  0  0  0  0  0  0  0  0  0
  vector<int>::iterator it;  

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

  it=set_union (first, first+5, second, second+5, v.begin());
                                               // 5 10 15 20 25 30 40 50  0  0
  cout << "union has " << int(it - v.begin()) << " elements.\n";
  return 0;
}

set用的时候

// set_union2 example
#include <set>
#include <iterator>
#include <iostream>
#include <algorithm>
using namespace std;  

int main(void)
{
    set<int> a,b,c;
    a.insert(1);
    a.insert(6);
    a.insert(6);
    b.insert(2);
    b.insert(6);
    b.insert(9);  

    //最后一个参数若使用c.begin()会产生编译错误assignment of read-only localtion.  

    set_union(a.begin(), a.end(), b.begin(), b.end(), inserter(c, c.begin()));
    copy(c.begin(), c.end(), ostream_iterator <int> (cout, " "));
    return 0;
}

vector用的时候

// set_union3 example
#include <vector>
#include <iterator>
#include <iostream>
#include <algorithm>
using namespace std;  

int main()
{
    vector<int> a,b,c;
    for(int e=0;e<10;e++)
    {
       a.push_back(e);
       b.push_back(e+5);
    }
    //最后一个参数若使用c.begin(),运行时会出错“Segmentation fault (core dumped)”.
    set_union(a.begin(),a.end(),b.begin(),b.end(),back_inserter(c));
    copy(c.begin(), c.end(), ostream_iterator<int> (cout, " "));
    return 0;
}