Creating a Pointer Array of Type Struct

Question

struct Vertex{
    int num;
    int low;
    bool seen;
    Vertex *parent;
    Vertex(){
        num = 0; low = 0; seen = false; parent = NULL;
    }
};

This is the struct. The problem is that when i attempt to make an array of type Vertex, the debugger states it's of non-pointer class type. This is how I declare it:

Vertex *mark;
mark = new Vertex[numVert];

(mark is declared in the class and the assignment is done in the default constructor).

I've declared pointer arrays exactly like this before. What would be the reason that it does not work now?

Graph::Graph(int v){
int i;
numVert = v;
count = 0;
mark = new Vertex[numVert];
matrix = new int*[numVert];
for (i=0;i<numVert;i++){
    mark[i]->seen = false;
    matrix[i] = new int[numVert];
    for (int j=0; j<numVert;j++)
        matrix[i][j]=0;
    }
}

This is where it is initially called. It states that it's of non-pointer type on both the assignment of the array and the assignment of its 'seen' member to false.

The two lines should work. Note that `mark[i]` has type `Vertex`. If you wanted `Vertex*` then the line should be `Vertex** mark = new Vertex*[numVert];`. — Karolis Juodelė, Oct 21 '12 at 19:29
Can you specify the exact error? along with which compiler you used? — StoryTeller - Unslander Monica, Oct 21 '12 at 19:37
Of course it doesn't work. mark is just a dynamic array of Vertex struct, not an array of pointers to Vertex. Use double star as Karolis said, or change to mark[i].seen = false. — SwiftMango, Oct 21 '12 at 19:40
This is horrible code. No offense meant, but please pick up [a decent C++ book](http://stackoverflow.com/q/388242/140719) and learn about `std::vector` and friends. — sbi, Oct 24 '12 at 06:57

score 2 · Accepted Answer · answered Oct 21 '12 at 19:33

The line

mark = new Vertex[numVert];

Allocates numVert objects in memory (calling the default constructor for each) and returns the address of the first object. In that regard your code is completely legit.

The debugger says that the object mark points to is not a pointer, which is correct (it's an array of objects).

Igor · Answer 2 · 2012-10-21T19:42:32.067

-3

Try this:

Vertex **mark[numVert]; 
mark = new Vertex *[numVert];

edited Oct 21 '12 at 19:42

answered Oct 21 '12 at 19:36

Igor

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This won't even compile. – Etienne de Martel Oct 21 '12 at 19:38

Creating a Pointer Array of Type Struct

2 Answers2