Segmentation fault error in BST - c

Question

I keep getting a segmentation fault error when I call the find_word function in my main.
when a word is added I want to return 1 and when it finds that word, I want it to return 1.
So I'm also not sure if my insert method is correct either.
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
struct node {
char *word;
struct node *left;
struct node *right;
};
static struct node *root;
int init(void)
{
struct node *new_node = malloc (sizeof(struct node));
if(new_node==NULL){
return 0;
}
else{
root = new_node;
new_node->left = NULL;
new_node->right = NULL;
return 1;
}
}
static int insert(struct node *newnode, char *word)
{
struct node *temp = NULL;
if(!(newnode))
{
temp = (struct node *)malloc(sizeof(struct node));
temp->left =NULL;
temp->right = NULL;
temp->word = word;
newnode = temp;
return 0;
}
if(word < (newnode)->word)
{
insert((newnode)->left, word);
}
else if(word > (newnode)->word)
{
insert((newnode)->right, word);
}
return 1;
}
int add_word(char *word)
{
return insert(root,word);
}
static int find(char *word, struct node *newnode){
if(newnode==NULL){
return 0;
}
else if(strcmp(word,newnode->word)>0){
find(word,newnode->left);
}
else if(strcmp(newnode->word,word)<0){
find(word,newnode->right);
}
else{
return 1;
}
return 0;
}
int find_word(char *word)
{
return find(word,root);
}
int main(int argc,char *argv[])
{
int k;
char l[5];
k = init();
printf("init: %d\n",k);
strcpy(l,"x");
k = add_word(l);
printf("add_word(%s): %d\n",l,k);
strcpy(l,"x");
k = find_word(l);
printf("find_word(%s): %d\n",l,k);
return 0;
}

Answer 1

to fix like this
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
struct node {
char *word;
struct node *left;
struct node *right;
};
static struct node *root = NULL;
static int insert(struct node **newnode, char *word){
struct node *temp = NULL;
int cmp;
if(!*newnode){
temp = (struct node *)malloc(sizeof(struct node));
temp->left =NULL;
temp->right = NULL;
temp->word = strdup(word);
*newnode = temp;
return 0;
}
if((cmp=strcmp(word, (*newnode)->word)) < 0)
return insert(&(*newnode)->left, word);
if(cmp > 0)
return insert(&(*newnode)->right, word);
return 1;
}
int add_word(char *word){
return insert(&root, word);
}
static int find(char *word, struct node *newnode){
int cmp;
if(newnode==NULL)
return 0;
if((cmp=strcmp(word, newnode->word)) == 0)
return 1;
if(cmp < 0)
return find(word, newnode->left);
return find(word, newnode->right);
}
int find_word(char *word){
return find(word, root);
}
int main(int argc,char *argv[]){
int k;
char *w;
k = add_word(w="x");
printf("add_word(%s): %d\n", w, k);
k = find_word(w);
printf("find_word(%s): %d\n", w, k);
return 0;
}

Answer 2

If newnode->word is NULL, you should insert the word at the current node, to handle the empty root node.
static int insert(struct node *newnode, char *word)
{
struct node *temp = NULL;
if(!(newnode))
{
temp = (struct node *)malloc(sizeof(struct node));
temp->left =NULL;
temp->right = NULL;
temp->word = malloc(strlen(word)+1);
strcpy(temp->word, word);
newnode = temp;
return 0;
}
if (newnode->word == NULL) {
newnode->word = malloc(strlen(word)+1);
strcpy(newnode->word, word);
return 1;
}
if(strcmp(word,(newnode)->word) < 0)
{
insert((newnode)->left, word);
}
else if(strcmp(word,(newnode)->word) > 0)
{
insert((newnode)->right, word);
}
return 1;
}
In your find function, you call strcmp twice. You swap the order of the arguments, but you also change > 0 to < 0. These cancel each other out, so both are testing the same thing. You need to change one or the other, but not both. You should also check for newnode->word == NULL.
static int find(char *word, struct node *newnode){
if(newnode==NULL || newnode->word == NULL){
return 0;
}
else if(strcmp(word,newnode->word)>0){
find(word,newnode->left);
}
else if(strcmp(word,newnode->word)<0){
find(word,newnode->right);
}
else{
return 1;
}
return 0;
}