C Program to Count Number of Leaf Nodes in a Tree

Code:

#include   stdio.h
#include   stdlib.h

struct btnode {
    int value;
    struct btnode * l;
    struct btnode * r;
};

typedef struct btnode bt;

bt *root;
bt *new, *list;
int count = 0;

bt * create_node();
void display(bt *);
void construct_tree();
void count_leaf(bt *);

void main()
{
    construct_tree();
    display(root);
    count_leaf(root);
    printf("\n leaf nodes are : %d",count);
}

/* To create a empty node */
bt * create_node()
{
    new = (bt *)malloc(sizeof(bt));
    new->l = NULL;
    new->r = NULL;
}

/* To construct a tree */
void construct_tree()
{
    root = create_node();
    root->value = 50;
    root->l = create_node();
    root->l->value = 20;
    root->r = create_node();
    root->r->value = 30;
    root->l->l = create_node();
    root->l->l->value = 70;
    root->l->r = create_node();
    root->l->r->value = 80;
    root->l->r->r = create_node();
    root->l->r->r->value = 60;
    root->l->l->l = create_node();
    root->l->l->l->value = 10;
    root->l->l->r = create_node();
    root->l->l->r->value = 40; 
}

/* To display the elements in a tree using inorder */
void display(bt * list)
{
    if (list == NULL)
    {
        return;
    }
    display(list->l);
    printf("->%d", list->value);
    display(list->r);
}

/* To count the number of leaf nodes */
void count_leaf(bt * list)
{
    if (list == NULL)
    {
        return;
    }
    if (list->l == NULL && list->r == NULL)
    {
        count++;
    }
    count_leaf(list->l);
    count_leaf(list->r);
}


Output:

        50
       /  \
     20    30
     / \    
   70    80
  /  \     \
 10     40      60

$ cc tree5.c
$ ./a.out
->10->70->40->20->80->60->50->30
 leaf nodes are : 4



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