C++ set的使用方法详解

我的代码如下：

#include<iostream> 
#include<set> 
#include<algorithm> 
#include<vector> 
using namespace std; 
void print(set<int> a) 
{ 
  if(a.begin() == a.end()) 
      cout << "}" << endl; 
  for(set<int>::iterator it = a.begin();it!=a.end();it++) 
  { 
    if(++it==a.end()) 
    { 
      it--; 
      cout << *it << "}n"; 
    } 
    else 
    { 
      it--; 
      cout << *it << ", "; 
    } 
  } 
} 
int main() 
{ 
  int T, cou = 0; 
  set<int> a, b, c; 
  cin >> T; 
  while(T--) 
  { 
    cou++; 
    a.clear(), b.clear(), c.clear(); 
    int n; 
    cin >> n; 
    for(int i=0;i<n;i++) 
    { 
      int x; 
      cin >> x; 
      a.insert(x); 
    } 
    cin >> n; 
    for(int i=0;i<n;i++) 
    { 
      int x; 
      cin >> x; 
      b.insert(x); 
    } 
    cout << "Case# " << cou << ":" << endl; 
    cout << "A = {"; 
    print(a); 
    cout << "B = {"; 
    print(b); 
    set_union(a.begin(),a.end(),b.begin(),b.end(),inserter(c,c.begin())); 
    cout << "A u B = {"; 
    print(c); 
    c.clear(); 
    set_intersection(a.begin(),a.end(),b.begin(),b.end(),inserter(c,c.begin())); 
    cout << "A n B = {"; 
    print(c); 
    c.clear(); 
    set_difference(a.begin(),a.end(),b.begin(),b.end(),inserter(c,c.begin())); 
    cout << "A - B = {"; 
    print(c); 
    c.clear(); 
    set_difference(b.begin(),b.end(),a.begin(),a.end(),inserter(c,c.begin())); 
    cout << "SA = {"; 
    print(c); 
    c.clear(); 
    set_difference(a.begin(),a.end(),b.begin(),b.end(),inserter(c,c.begin())); 
    cout << "SB = {"; 
    print(c); 
  } 
 
  return 0; 
}