Thread: Problems creating a tree

I am trying to create a tree that will represent an array of strings given the array of strings, the starting node, and the size of the array of strings.

Code:

e.g calling initialize tree with {"ab","ac","ace","act","aco","bd","b"} should be

                                a                                     b
                              /   \                                   |
                             c    b                                  d
                           /|\        
                        e  t o

I am getting warnings complaining about assignment from incompatible pointer types, but I don't understand where I went wrong.

Code:

	typedef struct{
		struct struct_node *child_next;
		struct struct_node *child_start;
		char data;
		int is_end;
	}struct_node;
	void initialize_tree(struct_node *tree, char **text, int size){
		void add_element(struct_node *tree, char *text, int i){
			if(text[i] == '\0')
				tree->is_end = 1;
			else if(tree->data == text[i] && tree->child_start != NULL){
				tree = tree->child_start;
				add_element(tree, text, ++i);
			}else if(tree->data != text[i] && tree->child_next != NULL){
				tree = tree->child_next;
				add_element(tree, text, ++i);
			}else if(tree->child_next == NULL
			|| (tree->data == text[i] && tree->child_start == NULL)){
				tree->child_next = malloc(sizeof(struct_node));
				tree = tree->child_next;
				tree->child_start = tree;
				tree->data = text[i];
				add_element(tree, text, ++i);
			}
		}
		struct struct_node *root = tree;
		int i = 0;
		while(i < size){
			add_element(tree, text[i], 0);
			tree = root;
			i++;
		}
	};

It's really confusing have a type named "struct_node", especially when mashing that into a typedef of the same name and trying to use "struct struct_node". You really should consider a better name. Just 'node' would be a big improvement.

Your problem is that you declare child_start to be of type struct struct_node, but there is no struct by that name. You have a nameless struct typedef'ed to struct_node. Try the following:

Code:

typedef struct struct_node {  // that 'struct_node' is the name of your struct
    struct struct_node *child_next;
    struct struct_node *child_start;
    char data;
    int is_end;
} struct_node;  // this one just creates a short hand for 'struct struct_node'

I generally prefer something like:

Code:

typedef struct node_s node_t;  // make 'node_t' a synonym for 'struct node_s'
struct node_s {  // declare my struct separate from the typedef, nice and clean
    node_t *child_next;
    ...
};

Also, don't put functions inside other functions, and drop that ; from the closing } of initialize_tree.