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Language: C++
Expertise: Intermediate

May 24, 2006

Sometimes you need a vector or list of associations. An association is a pair of values that has some link in the problem model. For example, a student and grade are associated with each other.

Suppose you want to maintain the grade of each student. You need a list of all the students together with their grades. This can be done by using <pair>, which is simply a struct with two values.

Here's the basic building block of a map:

vector<pair<string,int> > stu_gra;
string stu;
int gra;
do
{
   cin >> stu >> gra;
   stu_gra.push_back(pair<string,gra>(stu,gra) );
} while (stu != "end");

When you want to retrieve the values stored in the vector (or list) of pairs, you write:

vector<pair<string,int> > :: iterator i = stu_gra.begin();
while(i != stu_gra.end())
{
   cout << "Student : " << i->first << ", Grade : " << i->second << endl;
   i++;
}

The first and second members are used to access the respective elements of pair.