map，multimap，set，multiset

map中不允许两个相同的key存在，如果已经存在key1了，再插入key1将会失败，不管关联的value是否相同。multimap允许两个相同的key存在。对同一个key或是不同的key，二者都不管value是否相同。

同样的，set中不允许有相同的元素存在，multiset则允许。set和multiset都是有序的，插入新元素后会自动排序，默认是升序排列，也可以指定一个排序函数对象。

int multimap_test()
{
multimap<string, int> m;
m.insert(pair<string, int>("Jack", 1)); //����
m.insert(pair<string, int>("Jack", 2));
m.insert(pair<string, int>("Body", 1));
m.insert(pair<string, int>("Navy", 4));
m.insert(pair<string, int>("Demo", 3));
m.insert(pair<string, int>("Jack", 2));

multimap<string, int>::iterator iter;

for (iter = m.begin(); iter != m.end(); ++iter) //����
{
cout << (*iter).first << " " << (*iter).second << endl;
}

m.erase("Navy");

cout << "The element after delete:" << endl;

for (iter = m.begin(); iter != m.end(); ++iter)
{
cout << (*iter).first << " " << (*iter).second << endl;
}

int num = m.count("Jack");
iter = m.find("Jack");
int i;

cout << "the search result is:" << endl;

for (i = 1; i <= num; i++)
{
cout << (*iter).first << " " << (*iter).second << endl;
iter++;
}

if (i == 1)
{
cout << "can not find!" << endl;
}

return 0;
}

void set_test1()
{
set<int> set1;

for (int i = 0; i < 10; ++i)
{
set1.insert(i);
}

for (set<int>::iterator p = set1.begin(); p != set1.end(); ++p)
{
cout << *p << " ";
}

if (set1.insert(3).second) //把3插入到set1中
//插入成功则set1.insert(3).second返回1，否则返回0
//此例中，集中已经有3这个元素了，所以插入将失败
cout << "set insert success";

else
cout << "set insert failed";

int a[] = { 4, 1, 1, 1, 1, 1, 0, 5, 1, 0 };

multiset<int> A;

A.insert(set1.begin(), set1.end());

A.insert(a, a + 10);

cout << endl;

for (multiset<int>::iterator p = A.begin(); p != A.end(); ++p)
cout << *p << " ";

}

void set_test2()
{
struct MyCmp
{
bool operator ()(const string s1, const string s2)
{
return s1 > s2;
}
};

typedef set<string, MyCmp> TMySet;

TMySet stSet1;
stSet1.insert(string("sfdsfd"));
stSet1.insert(string("apple"));
stSet1.insert(string("english"));
stSet1.insert(string("dstd"));

cout << endl << "s1:" << endl;
TMySet::iterator it = stSet1.begin();
while (it != stSet1.end())
cout << *it++ << " ";

TMySet stSet2;
stSet2.insert(string("abc"));
stSet2.insert(string("apple"));
stSet2.insert(string("english"));

cout << endl << "s2:" << endl;
it = stSet2.begin();
while (it != stSet2.end())
cout << *it++ << " ";

cout << endl << endl;

string str[10];
string *end = set_intersection(stSet1.begin(), stSet1.end(), stSet2.begin(), stSet2.end(), str, MyCmp());//求交集，返回值指向str最后一个元素的尾端
cout<<"result of set_intersection s1,s2:"<<endl;
string *first = str;
while (first < end)
cout << *first++ << " ";

cout << endl << endl << "result of set_union of s1,s2" << endl;
end = set_union(stSet1.begin(), stSet1.end(), stSet2.begin(), stSet2.end(), str, MyCmp()); //并集
first = str;
while (first < end)
cout << *first++ << " ";
cout << endl << endl << "result of set_difference of s2 relative to s1" << endl;

// set_difference，该函数用于求两个集合（广义的集合，数组、vector等等都是的）的差集，结果集合中包含所有属于第一个集合但不属于第二个集合的元素
first = str;
end = set_difference(stSet1.begin(), stSet1.end(), stSet2.begin(), stSet2.end(), str, MyCmp());//s2相对于s1的差集
while(first<end)
cout << *first++ << " ";
cout << endl << endl << "result of set_difference of s1 relative to s2" << endl;

first = str;
end = set_difference(stSet2.begin(), stSet2.end(), stSet1.begin(), stSet1.end(), str, MyCmp());//s1相对于s2的差集
while (first < end)
cout << *first++ << " ";
cout << endl << endl;

first = str;
end = set_symmetric_difference(stSet1.begin(), stSet1.end(), stSet2.begin(), stSet2.end(), str, MyCmp());//上面两个差集的并集 while(first<end)
cout << *first++ << " ";
cout << endl;

}