Pfthb

I'm new to C programming, but what I'm trying to do is create a BST using arrays. Here is my code for the headers that I am using:

bst.h

#ifndef ASSIGNMENT4_BST_H
#define ASSIGNMENT4_BST_H

// ====== this is in bst.h
#include "data.h"
typedef struct Node *tree_nodes; unsigned char *is_free; int size; BStree_struct;
typedef BStree_struct* BStree;
BStree bstree_ini(int size);
void bstree_insert(BStree bst, Key *key, int data);
void bstree_traversal(BStree bst);
void bstree_free(BStree bst);

#endif //ASSIGNMENT4_BST_H

data.h

#ifndef ASSIGNMENT4_DATA_H
#define ASSIGNMENT4_DATA_H

typedef struct char *name; int id; Key;
typedef struct Key *key; int data; Node;
Key *key_construct(char *in_name, int in_id);
int key_comp(Key key1, Key key2);
void print_key(Key *key);
void print_node(Node node);

#endif //ASSIGNMENT4_DATA_H

And here is the code for my actual source files:

bst.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "bst.h"
// Input: ’size’: size of an array
// Output: a pointer of type BStree,
// i.e. a pointer to an allocated memory of BStree_struct type
// Effect: dynamically allocate memory of type BStree_struct
// allocate memory for a Node array of size+1 for member tree_nodes
// allocate memory for an unsigned char array of size+1 for member is_free
// set all entries of is_free to 1
// set member size to ’size’;

void bstree_insert_helper (BStree, Key *, int, int);

BStree bstree_ini(int size) 
 BStree bstree = (BStree*) malloc(sizeof(BStree));
 bstree->tree_nodes = (Node*) malloc(size+1 * sizeof(Node));
 bstree->is_free = (unsigned char *) malloc (size+1 * sizeof(unsigned char));
 memset (bstree->is_free, '1', size+1);
 for (int i = 0 ; i < size; i++)
// printf("%c", bstree->is_free[i]);
 
 return bstree;


// Input: ’bst’: a binary search tree
// ’key’: a pointer to Key
// ’data’: an integer
// Effect: ’data’ with ’key’ is inserted into ’bst’
// if ’key’ is already in ’bst’, do nothing
void bstree_insert(BStree bst, Key *key, int data) 
 bstree_insert_helper(bst, key, data, 1);


void bstree_insert_helper (BStree bst, Key *key, int data, int index)
 if (bst->is_free[index] == '1')
 bst->tree_nodes[index].key = key;
 bst->tree_nodes[index].data = data;
 bst->is_free[index] = '0';
 else 
 int value = key_comp(*key, *bst->tree_nodes[index].key);
 if (value < 0)
 int newIndex = 2*index;
 if (bst->is_free[newIndex] == '1')
 bst->tree_nodes[newIndex].key = key;
 bst->tree_nodes[newIndex].data = data;
 bst->is_free[newIndex] = '0';
 else 
 bstree_insert_helper(bst, key, data, newIndex);
 
 else if (value > 0)
 int newIndex = 2*index+1;
 if (bst->is_free[newIndex] == '1')
 bst->tree_nodes[newIndex].key = key;
 bst->tree_nodes[newIndex].data = data;
 bst->is_free[newIndex] = '0';
 else 
 bstree_insert_helper(bst, key, data, newIndex);
 
 else 
 puts("Key already exists... Aborting");
 
 


int main ()
 BStree bsTree = bstree_ini(10);
 bstree_insert_helper(bsTree, key_construct("Ilya", 1), 11, 1);
 bstree_insert_helper(bsTree, key_construct("Covin", 2), 12, 1);
 bstree_insert_helper(bsTree, key_construct("adolf", 3), 13, 1);
 bstree_insert_helper(bsTree, key_construct("henlo", 4), 14, 1);
 print_node(bsTree->tree_nodes[1]);
 return 0;

data.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "data.h"


// Input: ’in_name’: a string ends with ’’
// ’in_id’: an integer
// Output: a pointer of type pointer to Key,
// pointing to an allocated memory containing a Key
// Effect: dynamically allocate memory to hold a Key
// set Key’s id to be in_id
// dynamically allocate memory for the Key’s name
// so that name will contain what is in ’in_name’.
// Note: may use strdup()
Key *key_construct(char *in_name, int in_id) 
 Key *key = (Key*) malloc(sizeof(Key));
 key->name = strdup(in_name);
 key->id = in_id;
 return key;

// Input: ’key1’ and ’key2’ are two Keys
// Output: if return value < 0, then key1 < key2,
// if return value = 0, then key1 = key2,
// if return value > 0, then key1 > key2,
// Note: use strcmp() to compare key1.name and key2.name
// if key1.name = key2.name, then compare key1.id with key2.id
int key_comp(Key key1, Key key2) 

// Input: ’key’: a pointer to Key
// Effect: ( key->name key->id ) is printed
void print_key(Key *key) 
 char *name = key->name;
 int id = key->id;

 printf("%s, %i", name, id);


// Input: ’node’: a node
// Effect: node.key is printed and then the node.data is printed
void print_node(Node node) 
 printf("%s, %d n", node.key->name, node.data);

The issue is that when I run the print_node function in main in bst.c, I expect it to print the key.name and data for indices 1,2,3, and 7 in the array properly. However, the key.name for indices 1 and 3 are not printed properly. Instead, I get a bunch of gibberish that looks something like this - 0+@]�, 11 if I used print_node(bsTree->tree_nodes[1]). I have a feeling it has something to do with me incorrectly allocating memory for the keys in data.c but I cannot figure out exactly what I'm doing wrong.

I believe the error is here:

(size+1 * sizeof(Node))

inside BStree bstree_ini(int size):

bstree->tree_nodes = (Node*) malloc(size+1 * sizeof(Node));
bstree->is_free = (unsigned char *) malloc (size+1 * sizeof(unsigned char));
memset (bstree->is_free, '1', size+1);

* is executed first, then + (like in normal math), see operator precedence, the expression:

size+1 * sizeof(Node)

is equal to:

size + (1 * sizeof(Node))

which is not what you wanted!

Use proper braces:

malloc((size + 1) * sizeof(Node));

or use calloc:

calloc(sizeof(Node), size + 1);

Some friendly notices:

• Nice code!


• Please don't cast the result of malloc.


• 
  bstree->is_free would be clearer if it would be bool type. And it would be clearer (to me) if it would be bstree->is_used as I can expect it is initialized to zero on a new object, it would be also easy to clear it memset(bstree->is_used, 0, ...). You just assign '1' and '0' to it, I find boolean to be clearer for this indent, bstree->us_used[obj_num] = true; In the future you may go for a bit-container.