一、set
在了解关联容器set之前，让我们先来看看下面这个例子，并猜测该例子输出什么：
// stl/set1.cpp #include <iostream>
#include <set> int main()
{
//type of the collection
typedef std::set<int> IntSet; IntSet coll; //set container for int values /* insert elements from 1 to 6 in arbitray order
*- value 1 gets inserted twice
*/
coll.insert();
coll.insert();
coll.insert();
coll.insert();
coll.insert();
coll.insert();
coll.insert(); /* print all elements
*- iterate over all elements
*/
IntSet::const_iterator pos;
for (pos = coll.begin(); pos != coll.end(); ++pos) {
std::cout << *pos << ' ';
}
std::cout << std::endl;
}
其中，输出的结果为：1 2 3 4 5 6
下面，我们根据该输出结果对关联容器set做一个分析：
1. set元素的唯一性；
2. set默认按照从小到大排序；This type uses the default sorting criterion, which sorts the elements by using operator <.
如果你想要改变它的排序方法，需要传递额外的参数，例如：
typedef set<int,greater<int> > IntSet;
Note that you have to put a space between the two ">" characters. ">>" would be parsed as shift operator, which would result in a syntax error.
二、multiset
If you want to use a multiset rather than a set, you need only change the type of the container (the header file remains the same):
typedef multiset<int> IntSet;
A multiset allows duplicates, so it would contain two elements that have value 1. Thus, the output of the program would change to the following:
1 1 2 3 4 5 6 例如：
// stl/mmap1.cpp #include <iostream>
#include <map>
#include <string>
using namespace std; int main()
{
//type of the collection
typedef multimap<int, string> IntStringMMap; IntStringMMap coll; //set container for int/string values //insert some elements in arbitrary order
//- a value with key 1 gets inserted twice
coll.insert(make_pair(,"tagged"));
coll.insert(make_pair(,"a"));
coll.insert(make_pair(,"this"));
coll.insert(make_pair(,"of"));
coll.insert(make_pair(,"strings"));
coll.insert(make_pair(,"is"));
coll.insert(make_pair(,"multimap")); /* print all element values
*- iterate over all elements
*- element member second is the value
*/
IntStringMMap::iterator pos;
for (pos = coll.begin(); pos != coll.end(); ++pos) {
cout << pos->second << ' ';
}
cout << endl;
}