alberi binari

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

struct tree
{
    int x;
    struct tree *left;
    struct tree *right;
};

int altezza(struct tree*);
int numnodi(struct tree*);
struct tree *insabr(struct tree*,int);

int main()
{
    struct tree *root=NULL;
    printf("%d %d", altezza(root), numnodi(root));
    return 0;
}

int altezza(struct tree *root)
{
    int h1, h2;
    if(root==NULL)
        return -1;
    h1=altezza(root->left);
    h2=altezza(root->right);
    if(h1>h2)
        return h1+1;
    else
        return h2+1;
}

int numnodi(struct tree *root)
{
    int res=0, s1, s2;
    if(root!=NULL)
    {
        s1=numnodi(root->left);
        s2=numnodi(root->right);
        res=s1+s2+1;
    }
    return res;
}

struct tree *insabr(struct tree *root, int k)
{
    if(root==NULL)
    {
        root=(struct tree*)malloc(sizeof(struct tree));
        root->x=k;
        root->left=NULL;
        root->right=NULL;
    }
    else
    {
        if(k<root->x)
            root->left=insabr(root->left,k);
        else
            root->right=insabr(root->right,k);
    }
    return root;
};