How to declare and init two dimensional array of strings?

Question

i need something like this

const char **nodeNames[] = 
{
    {"RootNode", "Reference", "Node_1", "Node_2", "Node_3"},
    {"RootNode", "Hips", "Node_1", "Node_2", "Node_3"},
    {"RootNode", "Heviest", "Node_1", "Node_2", "Node_3"},
};

but with previous declaration, i got an error.

And how can i reference to it in code?

jrok · Accepted Answer · 2013-05-30 12:59:07Z

2

Looks like you want a two dimensional array of const char*:

const char *nodeNames[][5] =
{                 // ^^ this dimension can be deduced by the compiler, the rest not
    {"RootNode", "Reference", "Node_1", "Node_2", "Node_3"},
    {"RootNode", "Hips", "Node_1", "Node_2", "Node_3"},
    {"RootNode", "Heviest", "Node_1", "Node_2", "Node_3"}
};

Note that you need to explicitly specify all but the major dimension's size.

This doesn't behave exactly like a 3D array of chars because your strings are not all of the same size. I trust you're aware of that and you won't for example dereference nodeNames[0][2][7], which would go beyond the end of "Node_1".

edited May 30, 2013 at 12:59

answered May 30, 2013 at 12:52

jrok

55.5k10 gold badges114 silver badges146 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Mats Petersson · Accepted Answer · 2013-05-30 12:57:21Z

Depends a little bit on what you want. This will give you a 2D array of strings:

const char *nodeNames[][20] = 
{
    {"RootNode", "Reference", "Node_1", "Node_2", "Node_3"},
    {"RootNode", "Hips", "Node_1", "Node_2", "Node_3"},
    {"RootNode", "Heviest", "Node_1", "Node_2", "Node_3"},
};

This will give you an array of pointers to an array of strings.

const char *node1[] = {"RootNode", "Reference", "Node_1", "Node_2", "Node_3"};
const char *node2[] = {"RootNode", "Hips", "Node_1", "Node_2", "Node_3"};
const char *node3[] = {"RootNode", "Heviest", "Node_1", "Node_2", "Node_3"};

const char **nodeNames2[] = 
{
    node1,
    node2,
    node3,
};

Note that the two are subtly different, in that the first is stored within the array (so there is a contiguous storage of 3 * 20 pointers to the strings), where the second only stores the address to the first pointer in the array of pointers, which in turn point to the string. There is no contiguous storage, only three pointers.

In both cases, the pointers may be the same value, since the three instances "Node_1" may be represented by a single string.

For a proper 3D array of char:

const char nodeNames3[3][5][12] = 
{
    {"RootNode", "Reference", "Node_1", "Node_2", "Node_3"},
    {"RootNode", "Hips", "Node_1", "Node_2", "Node_3"},
    {"RootNode", "Heviest", "Node_1", "Node_2", "Node_3"},
};

This stores all the characters in contiguous memory, that is 3 * 5 * 12 bytes.

Collectives™ on Stack Overflow

How to declare and init two dimensional array of strings?

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related