c++ set_union set_intersection使用

自定义类型也可以构造set，但同样必须定义“小于”运算符，set中的元素从小到大排列好了

#include<iostream>
#include<string>
#include <set>
#include <algorithm>
using namespace std;
int main(){
set<int>a;
set<int>b;
set<int>x;
x.insert(1);
x.insert(2);
a.insert(5);
a.insert(6);
a.insert(7);
b.insert(4);
b.insert(6);
b.insert(8);
set<int>::iterator ip;
for(ip=a.begin();ip!=a.end();ip++){
cout << "A的集合为" << *ip;
}cout << endl;
for(ip=b.begin();ip!=b.end();ip++){
cout << "B的集合为" << *ip;
}cout << endl;
//目标集合X 从哪个位置插入 x.begin()从x的头开始插入
set_union(a.begin(),a.end(),b.begin(),b.end(),inserter(x,x.begin()));
for(ip=x.begin();ip!=x.end();ip++){
cout << "并集:" << *ip;
}cout << endl;

x.clear() ;


set_intersection(a.begin(),a.end(),b.begin(),b.end(),inserter(x,x.begin()));
for(ip=x.begin();ip!=x.end();ip++){
cout << "交集:" << *ip;
}
cout << endl;

x.clear();


set_difference(a.begin(),a.end(),b.begin(),b.end(),inserter(x,x.begin()));
for(ip=x.begin();ip!=x.end();ip++)
cout << "差集:" <<*ip;
cout <<endl; return 0;
}

 --------------------------------------------------------------------------

// set_intersection example
#include <iostream> // std::cout
#include <algorithm> // std::set_intersection, std::sort
#include <vector> // std::vector

int main () {
int first[] = {5,10,15,20,25};
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_intersection (first, first+5, second, second+5, ++v.begin());
// 10 20 0 0 0 0 0 0 0 0
v.resize(it-v.begin()); // 10 20

std::cout << "The intersection has " << (v.size()) << " elements: ";
for (it=v.begin(); it!=v.end(); ++it)
std::cout << ' ' << *it;
std::cout << ' ';

return 0;
}

------------------------

#include <algorithm>
#include <iostream>
#include <functional>
#include <cstring>
using namespace std;
int main() {
char *Alphabet = "abcdefghijklmnopqrstuvwxyz" ;
char *Vowels = "aeiou" ;
char *AlphaNum = "0123456789abcdef" ;
char result[45] ;
char *last ;

int lenA = strlen(Alphabet) ;
int lenV = strlen(Vowels ) ;
int lenAN = strlen(AlphaNum) ;

cout << "Alphabet = " << Alphabet << endl ;
cout << "Vowels = " << Vowels << endl ;
cout << "AlphaNum = " << AlphaNum << endl ;

cout << " using non-predicate versions" << endl ;

//non-predicate set_difference
last = set_difference(Alphabet, Alphabet+lenA,
AlphaNum, AlphaNum+lenAN,
result) ;
*last = 0 ;
cout << "set_difference(Alphabet, AlphaNum) = " << result << endl ;

//non-predicate set_intersection
last = set_intersection(Alphabet, Alphabet+lenA,
AlphaNum, AlphaNum+lenAN,
result) ;
*last = 0 ;
cout << "set_intersection(Alphabet, AlphaNum) = " << result << endl ;

//non-predicate set_symmetric_difference
last = set_symmetric_difference(Alphabet, Alphabet+lenA,
Vowels , Vowels +lenV,
result) ;
*last = 0 ;
cout << "set_symmetric_difference(Alphabet, Vowels) = " << result << endl ;

//non-predicate set_union
last = set_union(Alphabet, Alphabet+lenA,
AlphaNum, AlphaNum+lenAN,
result) ;
*last = 0 ;
cout << "set_union(Alphabet, AlphaNum) = " << result << endl ;

cout << " using predicate versions" << endl ;

//predicate set_difference
last = set_difference(Alphabet, Alphabet+lenA,
AlphaNum, AlphaNum+lenAN,
result , less<char>()) ;
*last = 0 ;
cout << "set_difference(Alphabet, AlphaNum) = " << result << endl ;

//predicate set_intersection
last = set_intersection(Alphabet, Alphabet+lenA,
AlphaNum, AlphaNum+lenAN,
result , less<char>()) ;
*last = 0 ;
cout << "set_intersection(Alphabet, AlphaNum) = " << result << endl ;

//predicate set_symmetric_difference
last = set_symmetric_difference(Alphabet, Alphabet+lenA,
Vowels , Vowels +lenV,
result , less<char>()) ;
*last = 0 ;
cout << "set_symmetric_difference(Alphabet, Vowels) = " << result << endl ;

//predicate set_union
last = set_union(Alphabet, Alphabet+lenA,
AlphaNum, AlphaNum+lenAN,
result , less<char>()) ;
*last = 0 ;
cout << "set_union(Alphabet, AlphaNum) = " << result << endl ;

return 0 ;
}