Simple C Help

[lems]

I'm trying to make a binary search tree/tree insert function and I'm getting a segment fault error. This is my first time coding in C.


#include <stdio.h>
#include <stdlib.h>

typedef struct tree_node {
int val;
struct tree_node *left;
struct tree_node *right;
} tree_node;

tree_node* tree_insert(tree_node *root, int n){
tree_node *node;

node->val = n;

if(root == NULL){
return node;
}

else if(n < root->val)
return root->left = tree_insert(root->left, n);
else{
return root->right = tree_insert(root->right, n);
}

}

here's my main:


#include <stdio.h>

typedef struct tree_node {
int val;
struct tree_node *left;
struct tree_node *right;
} tree_node;


tree_node* tree_insert(tree_node*, int);
int tree_sum(tree_node*);
main() {

tree_node *root;
int n = 0;


do{
printf("Enter an integer (type 0 to quit): ");
scanf("%d", &n);
root = tree_insert(root, n);
} while(n != 0);
}

[WW]

You are not allocating any memory for the tree_node structures. The first time your program executes "node->val = n" in tree_insert(), it will crash, because node does not point to memory containing a tree_node structure.

[Mr.Macdonald]

why are you returning the tree below. heres pseudo-ish code for insert


char insert(tree**, val) {
if (*tree == 0) {
*tree = mk_tree();
(*tree)->val = val;
return 1;
}
if (val < tree.val && tree.less != 0) {
insert(&(*tree)->less, val);
return 1;
}
else if (val > tree.val && tree.less != 0) {
insert(&(*tree)->more, val);
return 1;
}

if (val < tree.val && (*tree)->less == 0) {
(*tree)->less = mk_tree();
(*tree)->less->val = val
return 1;
}
else if (val > tree.val && (*tree)->more == 0) {
(*tree)->less = mk_tree();
(*tree)->less->val = val
return 1;
}
return 0;
}

First Implement in python and then try in C, It helps me!

[nitro_n2o]

whenever you create a pointer like tree_node *node you'll have to malloc it ..

change it to something like:

tree_nodo *node = (tree_node *)malloc(sizeof(tree_node));