Printing the structure of n-ary array in C - c

Question

My homework for my c course is to implement a menu as a n-ary tree. I have to create a struct, populate it with data and print the data.
Although creating a struct and populating were relatively easy, I have found the struggle with printing. My goal is to print the structure in this manner:
1 File
1.1 Open
1.2 Save As
1.3 Save as Other
1.3.1 Text
1.3.2 Word or Excel Online
1.4 Send File
1.4.1 Attach to Email
1.4.2 Send & Track
1.5 Close
My struggle is that I can't find a way how to:
a) Add spaces after each child.
b) Add number for each child of the child.
My structure looks like this:
typedef struct node
{
long nodeID;
long parentNodeID;
char name[100];
struct node *next;
struct node *child;
} node;
My failed attempt to accomplish this :
void printMenu(node* root){
if(root == NULL) {
fprintf(stderr, "Root has not been initialised");
exit(1);
}
if(root->parentNodeID == 0){
printf("%ld %s",root -> nodeID,root -> name);
fflush(stdout);
printMenu(root->child);
}
if(root->child){
printf("%6ld.%ld %s",root->parentNodeID,root->nodeID - 1,root->name);
fflush(stdout);
printMenu(root->child);
}
printf("%5ld.%ld %s",root->parentNodeID,root->nodeID - 1,root->name);
fflush(stdout);
printMenu(root -> next);
}
Please send help :(

Answer 1

I would sugggest using recursion. Below is a coded up example of how that would work. You would need to call this function with spacing starting at 0. This also assumes that the parentID is the appropriate ID with the previous parent id's.
void printMenu(node* root, int spacing) {
if(root == NULL) {
return;
}
else {
for(int i =0; i < spacing; i++) {
printf(' ');
}
printf("%d.%d %s", root->parentNodeID, root->nodeID, root->name);
for(int i =0; i< sizeof(root->child); i++) {
printNodes(root->child[i], spacing+1);
}
}
}

Answer 2

Rather than long parentNodeID, use a pointer to the parent node:
typedef struct node
{
struct node *parent;
struct node *next;
struct node *child;
char *name;
long id;
} node;
The root level nodes (File, for example) have NULL parents.
This lets you use a simple recursive function to print the IDs. The only trick is that you need to recurse before printing:
void print_path(FILE *out, node *to)
{
if (to->parent) {
/* Non-root nodes */
print_path(out, to->parent);
fprintf(out, ".%ld", to->id);
} else
/* Root nodes */
fprintf(out, "%ld", to->id);
}
With this, printing the menu recursively is easy:
void print_menu(FILE *out, node *menu, int indent)
{
while (menu != NULL) {
/* Print indent first */
fprintf(out, "%*s", indent, "");
/* Current menu entry */
print_path(out, menu);
fprintf(out, " %s\n", menu->name);
/* Submenu? */
if (menu->child)
print_menu(out, menu->child, 3 + indent);
menu = menu->next;
}
}
If you have say node *all; that contains your menu tree, and you wanted to print it to standard output, just call print_menu(stdout, all, 0);.
Note that I like to explicitly specify the file handle used for output, rather than just assume it is always stdout. (fprintf(stdout, ..FOOBAR..) is equivalent to printf(..FOOBAR..).) This approach lets me use the exact same functions when printing to a file, you see.
Printing the indent via %*s is not magic. The * in the width field for the s conversion just means that printf() will take the width from an int parameter, before the actual string to be printed. Thus, printf("%*s", n, "") will print n spaces. It is often called a "trick", but really, it is just well-documented printf() behaviour.