C program to print binary tree

C program to print binary tree

Binary Tree:

    5
 /    \
3      7
/ \     / \
      2   4  6   8
      /
  1

Output:

Inorder Traversal of the binary tree:
1 2 3 4 5 6 7 8
Preorder Traversal of the binary tree:
5 3 2 1 4 7 6 8
Postorder Traversal of the binary tree
1 2 4 3 6 8 7 5

Implementation:

/* binary tree is a kind of data structure which has either: no children one child two children For example: 5 / \ 3 7 / \ / \ 2 4 6 8 / 1 Is a binary tree. Node 1 has no children Node 2 has one child Node 2 has two children */ #include <stdio.h> /* defining the structure of the each node Each node will have a data which may point to one child or two child or no child For that we may need two pointers left & right to point to childrens if any or else NULL to indicate absence of child node */ struct node { int data; /* self referential pointers, left & right pointers shares the space with data in every structure node & used to store the address of another node which has the same structure definition as node does */ struct node *left,*right; }; /* function to allocate memory for the new node about to create and insert the data in it and assign the left & right pointers with NULL to indicate that there is no child for new node right now Last, return the address of the newly created node */ struct node* newnode(int data) { struct node *temp=(struct node*)malloc(sizeof(struct node)); temp->data=data; temp->left=NULL; temp->right=NULL; return temp; } /* call the function newnode: 1. sends the data to be inserted 2. gets back the address of the newly created node 3. returns the address of the newly created node to the called function */ struct node* insert(int data) { return newnode(data); } /* Inorder traversal of the binary tree Nodes will be printed in the following order: 1. Left Node 2. Root Node 3. Right Node */ void inorder(struct node *root) { if(root==NULL) return; /* recursively calls the same function until it reaches left most node of the tree */ inorder(root->left); /* start printing from the left most node */ printf("%d ",root->data); /* prints every right node after the left node & root node get printed */ inorder(root->right); } /* Preorder traversal of the binary tree Nodes will be printed in the following order: 1. Root Node 2. Left Node 3. Right Node */ void preorder(struct node *root) { /* If we reach a NULL node, return the control to the recursive function called */ if(root==NULL) return; /* Print the root data first */ printf("%d ",root->data); /* Recur for left nodes */ preorder(root->left); /* Recur for right nodes */ preorder(root->right); } /* Postorder Traversal of the binary tree Nodes gets printed in the following order: 1. Left Node 2. Right Node 3. Root Node */ void postorder(struct node *root) { if(root==NULL) return; postorder(root->left); postorder(root->right); printf("%d ",root->data); } int main(void) { struct node *root=NULL; /* Inserting the nodes in the binary tree in the following order 5 / \ 3 7 / \ / \ 2 4 6 8 / 1 */ root=insert(5); root->left=insert(3); root->left->left=insert(2); root->left->left->left=insert(1); root->left->right=insert(4); root->right=insert(7); root->right->left=insert(6); root->right->right=insert(8); printf("Inorder Traversal of the binary tree:\n"); inorder(root); printf("\nPreorder Traversal of the binary tree:\n"); preorder(root); printf("\nPostorder Traversal of the binary tree:\n"); postorder(root); return 0; }