Boundary_Traversal_of_binaryTree

C++ Questions/Boundary_Traversal_of_binaryTree

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+/* program for boundary traversal of a binary tree */
+#include <stdio.h>
+#include <stdlib.h>
+
+/* A binary tree node has data, pointer to left child
+   and a pointer to right child */
+struct node
+{
+    int data;
+    struct node *left, *right;
+};
+
+// A simple function to print leaf nodes of a binary tree
+void printLeaves(struct node* root)
+{
+    if ( root )
+    {
+        printLeaves(root->left);
+
+        // Print it if it is a leaf node
+        if ( !(root->left)  &&  !(root->right) )
+            printf("%d ", root->data);
+
+        printLeaves(root->right);
+    }
+}
+
+// A function to print all left boundry nodes, except a leaf node.
+// Print the nodes in TOP DOWN manner
+void printBoundaryLeft(struct node* root)
+{
+    if (root)
+    {
+        if (root->left)
+        {
+            // to ensure top down order, print the node
+            // before calling itself for left subtree
+            printf("%d ", root->data);
+            printBoundaryLeft(root->left);
+        }
+        else if( root->right )
+        {
+            printf("%d ", root->data);
+            printBoundaryLeft(root->right);
+        }
+        // do nothing if it is a leaf node, this way we avoid
+        // duplicates in output
+    }
+}
+
+// A function to print all right boundry nodes, except a leaf node
+// Print the nodes in BOTTOM UP manner
+void printBoundaryRight(struct node* root)
+{
+    if (root)
+    {
+        if ( root->right )
+        {
+            // to ensure bottom up order, first call for right
+            //  subtree, then print this node
+            printBoundaryRight(root->right);
+            printf("%d ", root->data);
+        }
+        else if ( root->left )
+        {
+            printBoundaryRight(root->left);
+            printf("%d ", root->data);
+        }
+       // do nothing if it is a leaf node, this way we avoid
+       // duplicates in output
+    }
+}
+
+
+// A function to do boundary traversal of a given binary tree
+void printBoundary (struct node* root)
+{
+    if (root)
+    {
+        printf("%d ",root->data);
+
+        // Print the left boundary in top-down manner.
+        printBoundaryLeft(root->left);
+
+        // Print all leaf nodes
+        printLeaves(root->left);
+        printLeaves(root->right);
+
+        // Print the right boundary in bottom-up manner
+        printBoundaryRight(root->right);
+    }
+}
+
+// A utility function to create a node
+struct node* newNode( int data )
+{
+    struct node* temp = (struct node *) malloc( sizeof(struct node) );
+
+    temp->data = data;
+    temp->left = temp->right = NULL;
+
+    return temp;
+}
+
+// Driver program to test above functions
+int main()
+{
+    // Let us construct the tree given in the above diagram
+    struct node *root         = newNode(20);
+    root->left                = newNode(8);
+    root->left->left          = newNode(4);
+    root->left->right         = newNode(12);
+    root->left->right->left   = newNode(10);
+    root->left->right->right  = newNode(14);
+    root->right               = newNode(22);
+    root->right->right        = newNode(25);
+
+    printBoundary( root );
+
+    return 0;
+}