Added Boundary Traversal

Author: Aakash Kumar

Trees/Boundary-Traversal.cpp

@@ -0,0 +1,105 @@
+/*
+The Problem is to print Boundary elements of a binary tree
+For Example, Lets say our tree is 
+                      0
+                   /     \
+                  5       6 
+                / \      /  \
+               9    65  7   10
+             /  \  /  \
+            8   12 1    98
+
+            Then its output should be
+            0->5->9->8->12->1->98->7->10->6
+
+            My approach for this problem is to split this problem into three simpler problems
+            1. Printing the Left Part of boundary ( excluding the leaf in left part)
+            2. Printing the leaves of tree
+            3. Printing the right part in bottom up manner ( excluding the leaf in right part)
+
+*/
+#include <iostream>
+#include <stack>
+using namespace std;
+template <typename T>
+struct TreeNode
+{
+    T val;
+    TreeNode *left;
+    TreeNode *right;
+    TreeNode(T vl) // This Constructor helps in Creating a new Tree node with value vl
+    {
+        val = vl;
+        left = NULL;
+        right = NULL;
+    }
+    TreeNode(T vl, TreeNode *lft, TreeNode *rt)
+    {
+        val = vl;
+        left = lft;
+        right = rt;
+    }
+    void addChilds(T lVal, T rVal)
+    {
+        TreeNode *lft = new TreeNode(lVal);
+        TreeNode *rt = new TreeNode(rVal);
+        left = lft;
+        right = rt;
+    }
+};
+
+template <typename T>
+void printLeftPart(TreeNode<T> *root)
+{
+    if (root == NULL)
+        return;
+    if (root->left == NULL && root->right == NULL)
+        return;
+    cout << root->val << " ";
+    printLeftPart(root->left);
+}
+template <typename T>
+void printRightPart(TreeNode<T> *root)
+{
+    if (root == NULL)
+        return;
+    if (root->left == NULL && root->right == NULL)
+        return;
+    printRightPart(root->right);
+    cout << root->val << " ";
+}
+template <typename T>
+void printLeaves(TreeNode<T> *root)
+{
+    if (root == NULL)
+        return;
+    if (root->left == NULL && root->right == NULL)
+    {
+        cout << root->val << " ";
+        return;
+    }
+    printLeaves(root->left);
+    printLeaves(root->right);
+}
+template <typename T>
+void printBoundary(TreeNode<T> *root)
+{
+    cout << "Boundary Elements are : ";
+    printLeftPart(root);
+    printLeaves(root);
+    printRightPart(root->right);
+    cout << "\n";
+}
+int main()
+{
+    TreeNode<int> root(0);
+    root.addChilds(5, 6);
+    root.left->addChilds(9, 65);
+    root.left->left->addChilds(8, 12);
+    root.left->right->addChilds(1, 98);
+    root.right->addChilds(7, 10);
+    printBoundary(&root);
+    //cout << root.val << " " << root.left->val << " " << root.right->val;
+    //printInorder(&root);
+    return 0;
+}