binary tree in C

int count(node *head)
{
    if(head == NULL) return 0;

    return count(head->left) + 1 + count(head->right);
}

int depth(node *head)
{
    if(head == NULL)
        return 0;
    else
    {
        int ldepth = depth(head->left);
        int rdepth = depth(head->right);

        if(ldepth < rdepth) return rdepth+1;
        else return ldepth+1;
    }
}

int compare(node *n1, node *n2)
{
    if(n1==NULL && n2==NULL)
        return true;
    else if(n1!=NULL && n2!=NULL)
    {
        return ((n1->val==n2->val) &&
            compare(n1->left, n2->left) &&
            compare(n1->right, n2->right));
    }
    else return false;
}

-----------------btree.c-----------------
#include <stdio.h>
#include <stdlib.h>

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


void print(node *head)
{
    if(head == NULL) return;

    print(head->left);
    printf("%d->",head->val);
    print(head->right);
}

node * insert(node *head, int val)
{
    if(head == NULL)
    {
        head = (node*)malloc(sizeof(node));
        head->left=head->right=NULL;
        head->val = val;
    }
    else if(val < head->val)
        head->left = insert(head->left, val);
    else if(val > head->val)
        head->right = insert(head->right, val);
    else
        printf("duplicate vale (%d)\n", val);

    return head;
}

int count(node *head)
{
    if(head == NULL) return 0;

    return count(head->left) + 1 + count(head->right);
}

int count2(node *head)
{
    int count = 0;

    if(head == NULL) return 0;
    count += count2(head->left);
    count += count2(head->right);

    return ++count;
}

void count3(node *head, int *count)
{
    if(head == NULL) return;

    count3(head->left, count);
    count3(head->right, count);
    (*count)++;
}

int depth(node *head)
{
    if(head == NULL)
        return 0;
    else
    {
        int ldepth = depth(head->left);
        int rdepth = depth(head->right);

        if(ldepth < rdepth) return rdepth+1;
        else return ldepth+1;
    }
}

#define true 1
#define false 0
int compare(node *n1, node *n2)
{
    if(n1==NULL && n2==NULL)
        return true;
    else if(n1!=NULL && n2!=NULL)
    {
        return ((n1->val==n2->val) &&
            compare(n1->left, n2->left) &&
            compare(n1->right, n2->right));
    }
    else return false;
}

int main()
{
    node *head1 = NULL;
    node *head2 = NULL;
    int c1 = 0;

    head1 = insert(head1, 50);
    insert(head1, 40);
    insert(head1, 70);
    insert(head1, 30);
    insert(head1, 25);
    insert(head1, 90);
    insert(head1, 45);
    insert(head1, 10);
    insert(head1, 55);
    insert(head1, 85);
    print(head1); printf("NULL\n");

    head2 = insert(head2, 50);
    insert(head2, 40);
    insert(head2, 70);
    insert(head2, 30);
    insert(head2, 25);
    insert(head2, 90);
    insert(head2, 45);
    insert(head2, 10);
    insert(head2, 55);
    insert(head2, 85);
    print(head2); printf("NULL\n");

    printf("number of nodes in the tree is %d\n", count(head1));
    printf("Max depth of the tree is %d\n", depth(head1));
    printf("comparison for both the tree is \"%s\"\n",
                compare(head1, head2)?"true":"false");

    return 0;
}
-----------------------------------------

Reference:
http://cslibrary.stanford.edu/110/BinaryTrees.html