Finding Preorder, Inorder and Postorder of binary tree in C Language

                  In this post, we will see sample program in C language to find preorder, inorder and postorder traversal of binary tree.
                  Preorder, inorder, postorder traversal follows the following traversal.
Preorder Traversal: Root-Left-Right
Inorder Traversal: Left-Root-Right
Postorder Traversal: Left-Right-Root 

                  Go through the following program:



Program: (treetraversal.c)

#include<stdlib.h> #include<stdio.h> /* We will consider Strict Binary Tree where each node has zero or two children */ struct binarytree { char data; struct binarytree *left, *right; }; typedef struct binarytree node; /* insertnode() and insert() functions are for adding nodes to tree */ void insertnode(node **tree,char val) { node *temp = NULL; if(!(*tree))     {         temp = (node *)malloc(sizeof(node));         temp->left = temp->right = NULL;         temp->data = val;         *tree = temp;     } } void insert(node **tree,char val) {     char l,r;     int numofchildren;     insertnode(tree, val);     printf("\nEnter number of children of %c:",val);     scanf("%d",&numofchildren);   if(numofchildren==2)    {     printf("\nEnter Left Child of %c:",val);     scanf("%s",&l);     insertnode(&(*tree)->left,l);     printf("\nEnter Right Child of %c:",val);     scanf("%s",&r);     insertnode(&(*tree)->right,r);       insert(&(*tree)->left,l);     insert(&(*tree)->right,r);    } } /* function preorder() will print preorder of nodes. */ void preorder(node * tree) {     if (tree)     {         printf("%c  ",tree->data);     preorder(tree->left);         preorder(tree->right);     } } /* function inorder() will print inorder of nodes. */ void inorder(node * tree) {     if (tree)     {         inorder(tree->left);         printf("%c  ",tree->data);         inorder(tree->right);     } } /* function postorder() will print inorder of nodes. */ void postorder(node * tree) {     if (tree)     {         postorder(tree->left);         postorder(tree->right);     printf("%c  ",tree->data);     } } /* deletetree() will free the memory allocated for tree */ void deletetree(node * tree) {     if (tree)     {         deletetree(tree->left);         deletetree(tree->right);         free(tree);     } } /* Program execution will start from main() function */ void main() {     node *root;     root = NULL;     node *tmp;     char val;     int i,temp;        /* Inserting nodes into tree(DAG) */     printf("\nEnter root of tree:");     scanf("%c",&val);     insert(&root,val);     /* Printing preorder of nodes of tree(DAG) */     printf("\nPreorder Display:\n");     preorder(root);     /* Printing inorder of nodes of tree(DAG) */     printf("\nInorder Display:\n");     inorder(root);     /* Printing postorder of nodes of tree(DAG) */     printf("\nPostorder Display:\n");     postorder(root);     printf("\n");              /* Deleting all nodes of tree */     deletetree(root); }

How To Run:
To Compile:
>>>gcc treetraversal.c

To Run:
>>>./a.out

Output:

For above tree, Preorder, Inorder and Postorder will be found out as follows:

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