BFS Traversal of a Binary Tree in C - c

Question

While I know there are cleaner more efficient programs out there for BFS traversal in other languages, in c it gets a bit lengthy
I've found some really lengthy and complicated programs on leetcode, as a beginner those are a little hard to understand, while I understand the basic concept behind it I found a much simpler and cleaner code here sanfoundry
but it doesn't work for some reason? I'd be grateful if someone can help me out with this :)
#include <stdio.h>
#include <stdlib.h>
struct btnode
{
int value;
struct btnode *left, *right;
};
typedef struct btnode node;
/* function declarations */
void insert(node *, node *);
void bfs_traverse(node *);
/*global declarations */
node *root = NULL;
int val, front = 0, rear = -1, i;
int queue[20];
void main()
{
node *new = NULL ;
int num = 1;
printf("Enter the elements of the tree(enter 0 to exit)\n");
while (1)
{
scanf("%d", &num);
if (num == 0)
break;
new = malloc(sizeof(node));
new->left = new->right = NULL;
new->value = num;
if (root == NULL)
root = new;
else
{
insert(new, root);
}
}
printf("elements in a tree in inorder are\n");
queue[++rear] = root->value;
bfs_traverse(root);
for (i = 0;i <= rear;i++)
printf("%d -> ", queue[i]);
printf("%d\n", root->right->right->right->value);
}
/* inserting nodes of a tree */
void insert(node * new , node *root)
{
if (new->value>root->value)
{
if (root->right == NULL)
root->right = new;
else
insert (new, root->right);
}
if (new->value < root->value)
{
if (root->left == NULL)
root->left = new;
else
insert (new, root->left);
}
}
/* displaying elements using BFS traversal */
void bfs_traverse(node *root)
{
val = root->value;
if ((front <= rear)&&(root->value == queue[front]))
{
if (root->left != NULL)
queue[++rear] = root->left->value;
if (root->right != NULL || root->right == NULL)
queue[++rear] = root->right->value;
front++;
}
if (root->left != NULL)
{
bfs_traverse(root->left);
}
if (root->right != NULL)
{
bfs_traverse(root->right);
}
}

Answer 1

I suggest implementing a queue of type btnode *
btnode *queue[20]; // I assume 20 is enought for what you need
...
void bfs_traverse(node *root) {
val = root->val;
if (front <= rear)
{
if (root->left != NULL)
queue[++rear] = root->left;
if (root->right != NULL)
queue[++rear] = root->right;
bfs_traverse(queue[front++]);
}
}
However, I would rather implement it using while. It's much cleaner than a recursive function. I would use recursiveness for DFS