Solution

CMakeLists.txt

@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.21)
+project(tree_preorder_traversal)
+
+set(CMAKE_CXX_STANDARD 14)
+
+add_executable(tree_preorder_traversal main.cpp)

main.cpp

@@ -0,0 +1,109 @@
+#include <iostream>
+#include <cstddef>
+#include <deque>
+
+class Node {
+    public:
+        int data;
+        Node *left;
+        Node *right;
+        Node(int d) {
+            data = d;
+            left = NULL;
+            right = NULL;
+        }
+};
+
+class Solution {
+    public:
+  		Node* insert(Node* root, int data) {
+            if(root == NULL) {
+                return new Node(data);
+            } else {
+                Node* cur;
+                if(data <= root->data) {
+                    cur = insert(root->left, data);
+                    root->left = cur;
+                } else {
+                    cur = insert(root->right, data);
+                    root->right = cur;
+                }
+
+               return root;
+           }
+        }
+
+/* you only have to complete the function given below.
+Node is defined as
+
+class Node {
+    public:
+        int data;
+        Node *left;
+        Node *right;
+        Node(int d) {
+            data = d;
+            left = NULL;
+            right = NULL;
+        }
+};
+
+*/
+
+//    void preOrder(Node *root) {
+//        /* #include <deque> */
+//        std::deque<Node*> q {root};
+//
+//        while (!q.empty()) {
+//            auto elem = q.back();
+//
+//            q.pop_back();
+//
+//            while (elem != nullptr) {
+//                if (elem->right != nullptr) {
+//                    q.push_back(elem->right);
+//                }
+//
+//                std::cout << elem->data << " ";
+//
+//                elem = elem->left;
+//            }
+//        }
+//    }
+
+    void printLeft(Node *left, Node *right) {
+
+        while (left != nullptr) {
+            std::cout << " " << left->data;
+
+            if (left->right != nullptr) {
+                printLeft(left->left, left->right);
+                break;
+            }
+
+            left = left->left;
+        }
+
+        if (right != nullptr) {
+            std::cout << " " << right->data;
+
+            printLeft(right->left, right->right);
+        }
+    }
+
+    void preOrder(Node *root) {
+        if (root == nullptr) {
+            return;
+        }
+
+        std::cout << root->data;
+
+        printLeft(root->left, root->right);
+    }
+
+}; //End of Solution
+
+int main() {
+    std::cout << "Hello, World!" << std::endl;
+    return 0;
+}