How to calculate the total number of nodes in a binary tree

Question

I need to calculate the total number of nodes in a binary tree. The problem occurs when I execute this code, providing the garbage value for the total number of nodes. The result of my program is similar to 993814. which should be 7.

How to solve this problem?

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

struct binarytree
{
    int data;
    struct binarytree * right, * left;
};

typedef struct binarytree node;

void insert(node ** tree, int val)
{
    node *temp = NULL;
    if(!(*tree))
    {
        temp = (node *)malloc(sizeof(node));
        temp->left = temp->right = NULL;
        temp->data = val;
        *tree = temp;
        return;
    }

    if(val < (*tree)->data)
    {
        insert(&(*tree)->left, val);
    }
    else if(val > (*tree)->data)
    {
        insert(&(*tree)->right, val);
    }

}

void print_preorder(node * tree)
{
    if (tree)
    {
        printf("%d\n",tree->data);
        print_preorder(tree->left);
        print_preorder(tree->right);
    }

}

void print_inorder(node * tree)
{
    if (tree)
    {
        print_inorder(tree->left);
        printf("%d\n",tree->data);
        print_inorder(tree->right);
    }
}

int count(node *tree)
{
    int c=0;

    if (tree ==NULL)
        return 0;

    else
    {
        c += count(tree->left);
        c += count(tree->right);
        return c;
    }
}

void print_postorder(node * tree)
{
    if (tree)
    {
        print_postorder(tree->left);
        print_postorder(tree->right);
        printf("%d\n",tree->data);
    }
}

int main()
{
    node *root;
    node *tmp;
    int c;

    root = NULL;
    /* Inserting nodes into tree */
    insert(&root, 9);
    insert(&root, 10);
    insert(&root, 15);
    insert(&root, 6);
    insert(&root, 12);
    insert(&root, 17);
    insert(&root, 2);

    /* Printing nodes of tree */
    printf("Pre Order Display\n");
    print_preorder(root);

    printf("In Order Display\n");
    print_inorder(root);

    printf("Post Order Display\n");
    print_postorder(root);

    printf("Number of node %d \n",c);

}

Answer 1

You declare c, but do not initialize anywhere and also do not use anywhere. Then you print a value cthat gives you the value for the garbage.

You can fix your function count(node *tree)as

int count(node *tree)
{
    int c =  1;             //Node itself should be counted
    if (tree ==NULL)
        return 0;
    else
    {
        c += count(tree->left);
        c += count(tree->right);
        return c;
    }
}

add main

int main()
{
    .............
    .............


    c = count(root);        //number of node assign to c
    printf("Number of node %d \n",c);
}

Answer 2

, .

int count(struct node *root){
    if(root == NULL){
        return 0;
    }
    else{
        return 1 + count(root->left) + count(root->right);
    }
}