Suppose we want to create a class for Graph. The class stores adjacency matrix representation of the graph. Therefore, our class structure would be something like below.
error: invalid use of non-static data member 'Graph::V'.
Even if we make V static, we get error “array bound is not an integer constant”
C++ doesn’t allow to create an stack allocated array in a class whose size is not constant. So we need to dynamically allocate memory. Below is a simple program to show how to dynamically allocate 2D array in a C++ class using a class for Graph with adjacency matrix representation.
0 1 1 0 0 0 1 0 1 0 0 1 0 0 0 1
A note on call of memset():
memset() is used separately for individual rows. We can’t replace these calls with one call because rows are allocated at different addresses and making a memset call like below would be disastrous.
// Wrong!! (Rows of matrix at different addresses) memset(adj, false, V*V*sizeof(bool));
This article is contributed by Dheeraj Gupta. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above
GeeksforGeeks has prepared a complete interview preparation course with premium videos, theory, practice problems, TA support and many more features. Please refer Placement 100 for details
- How to create an unordered_map of user defined class in C++?
- Program to create Custom Vector Class in C++
- How to create an unordered_set of user defined class or struct in C++?
- What are the data types for which it is not possible to create an array?
- Array of Strings in C++ (5 Different Ways to Create)
- Array class in C++
- Difference between Base class and Derived class in C++
- How to convert a class to another class type in C++?
- Where is an object stored if it is created inside a block in C++?
- What is Dynamic Memory Allocation?
- Dynamic Constructor in C++ with Examples
- C | Dynamic Memory Allocation | Question 6
- C | Dynamic Memory Allocation | Question 7
- C | Dynamic Memory Allocation | Question 8
- C | Dynamic Memory Allocation | Question 1