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Code Binary Tree

# Flatten binary tree in order of postorder traversal in c

C program for Flatten binary tree in order of postorder traversal. Here mentioned other language solution.

``````// Include header file
#include <stdio.h>
#include <stdlib.h>
/*
C program for
Flatten binary tree in order of post-order traversal
*/

// Node of Binary Tree
typedef struct TreeNode
{
// Define useful field of TreeNode
int data;
struct TreeNode * left;
struct TreeNode * right;
}TreeNode;

TreeNode * getTreeNode(int data)
{
// Create dynamic memory of TreeNode
TreeNode * ref = (TreeNode * ) malloc(sizeof(TreeNode));
if (ref == NULL)
{
// Failed to create memory
return NULL;
}
// Set node value
ref->data = data;
ref->left = NULL;
ref->right = NULL;
return ref;
}

typedef struct BinaryTree
{
// Define useful field of BinaryTree
struct TreeNode * root;
struct TreeNode * back;
}BinaryTree;

BinaryTree * getBinaryTree()
{
// Create dynamic memory of BinaryTree
BinaryTree * ref = (BinaryTree * ) malloc(sizeof(BinaryTree));
if (ref == NULL)
{
// Failed to create memory
return NULL;
}
// Set initial tree root to null
ref->root = NULL;
ref->back = NULL;
return ref;
}
// Recursive function
// Display postorder view of binary tree
void postOrder(TreeNode * node)
{
if (node != NULL)
{
postOrder(node->left);
postOrder(node->right);
// Print node value
printf("  %d", node->data);
}
}
// This are flattening tree nodes in postorder from
void transform(BinaryTree * ref, TreeNode * node)
{
if (node != NULL)
{
// Recursive executing left and right subtree
transform(ref,node->left);
transform(ref,node->right);
if (ref->back == NULL)
{
// This is first node of postorder traversal
// Get first node of transform tree
ref->root = node;
}
else
{
// Next node
ref->back->right = node;
// We taking only one direction
ref->back->left = NULL;
}
ref->back = node;
}
}
// This are handling the request of
// flatten tree nodes in post order from.
void flattenNode(BinaryTree * ref)
{
if (ref->root == NULL)
{
// When empty tree
return;
}
// Set back node
ref->back = NULL;
// Perform flatten operation
transform(ref,ref->root);
if (ref->back != NULL)
{
// Set last node of post order
ref->back->left = NULL;
ref->back->right = NULL;
}
ref->back = NULL;
}
// Display flatten elements of tree
void showElement(BinaryTree * ref)
{
if (ref->root == NULL)
{
printf("\n Empty Tree");
return;
}
printf("\n Flatten Tree Node in Postorder : \n");
TreeNode * temp = ref->root;
// Iterate tree elements
while (temp != NULL)
{
// Display node value
printf("  %d", temp->data);
// Visit to next node
temp = temp->right;
}
}
int main()
{
// New tree
BinaryTree * tree = getBinaryTree();
/*
Construct Binary Tree
-----------------------
1
/ \
/   \
6     8
/ \   / \
2   3 7   5
/   /   \   \
9   4    -6   11
*/
tree->root = getTreeNode(1);
tree->root->left = getTreeNode(6);
tree->root->left->left = getTreeNode(2);
tree->root->right = getTreeNode(8);
tree->root->right->right = getTreeNode(5);
tree->root->right->left = getTreeNode(7);
tree->root->right->left->right = getTreeNode(-6);
tree->root->left->right = getTreeNode(3);
tree->root->left->right->left = getTreeNode(4);
tree->root->left->left->left = getTreeNode(9);
tree->root->right->right->right = getTreeNode(11);
// Display tree elements
printf("\n Postorder Nodes : \n");
postOrder(tree->root);
// Testing
flattenNode(tree);
// After transform
showElement(tree);
return 0;
}``````

Output

`````` Postorder Nodes :
9  2  4  3  6  -6  7  11  5  8  1
Flatten Tree Node in Postorder :
9  2  4  3  6  -6  7  11  5  8  1``````

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