Converting a Tree to an Array-CodePudding

I'm trying to convert a BST to an Array.

void treeToArr(Node *root, int *ptr, int index)
{
if (root == NULL) {
    return;
}

storeInArray(root->left,ptr,index);
ptr[index  ] = root->value;
storeInArray(root->right,ptr,index);
}

When running this, I noticed that the index number kept changing, it went from 0 to 1 to 0 to 1 to 2 to 3. I just want it to increase normally [1,2,3,4..]. I'm new to C and i'm unsure why it's doing this.

Note that when I call this function, index is 0.

CodePudding user response：

You need to pass a pointer to index instead of index itself. That way, index will be modified across all recursive calls.

CodePudding user response：

It's one thing to pass values 'down' in recursive calls.
You could use a pointer to a single instance of an int index; that exists in the top level caller.
Or, you could return to 'parent nodes' what the child nodes have done with the value.

int treeToArr(Node *root, int *ptr, int index)
{
    if (root == NULL)
        return index;

    index = storeInArray(root->left,ptr,index);
    ptr[index  ] = root->value;
    return storeInArray(root->right,ptr,index);
}