How to Use the Vector STL Container Class

A container class is a class whose instances contain other classes. The Standard Template Library (STL) for C++ is available on the STL home webpage and consists of associative containers, sequences, strings and more. The vector class is a sequence and like all of the container classes, it is a template that may contain any object type. The following steps explain how to use this vector STL container class.

Instructions

1. Study what the vector class does. It supports insertion and deletion of its elements and random access to those elements. A vector's memory is managed automatically managed and its elements may vary dynamically.

2. Know where vector is defined. It is in a standard header called vector and a nonstandard header called vector.h which is included for backward-compatibility.

3. Learn the syntax for the vector class. It is Vector where T is the type of object to be stored in the vector and Alloc is number of elements to allocate memory.

4. Look at the following example for a simple use of the vector class:

   //declare the vector
   vector test(3);
   v[0] = 5;
   v[1] = v[0] + 2;
   //v[2] = 5 + 2 = 7
   v[2] = v[0] +v[1];
   // v[0] = 7, v[1] = 2, v[2] = 5
   reverse(v.begin(),v.end());

   Note vector is used the same as an ordinary array without having to allocate memory.

5. Observe the use of reverse in the last line of the code in Step 4. This function takes a range of elements (the entire vector v in this case) and reverses their order.

Resources

• Learn more about the Standard Template Library.