Update binary_search_tree.cpp

1. Memory Management:
Used std::unique_ptr for automatic memory management, reducing the risk of memory leaks.

2. STL Utilization:
Replaced the custom queue implementation with std::queue, simplifying breadth-first traversal.

3. Code Structure:
Organized the code into a BinaryTree class, encapsulating the tree functionality and providing clearer interfaces for operations.

4. Redundancy Reduction:
Combined logic for finding and removing nodes to reduce redundancy, improving readability and maintainability.

5. Error Handling:
Added checks to handle cases where nodes may not be present during removal and traversal.

data_structures/binary_search_tree.cpp

@@ -7,168 +7,189 @@
  * utilize any of the C++ STL features.
  */
 #include <iostream>
+#include <memory>
+#include <vector>
+#include <queue>
 
-struct node {
+// Node structure representing each element in the binary tree
+struct Node {
     int val;
-    node *left;
-    node *right;
-};
+    std::unique_ptr<Node> left;   // Using unique_ptr for automatic memory management
+    std::unique_ptr<Node> right;
 
-struct Queue {
-    node *t[100];
-    int front;
-    int rear;
+    Node(int value) : val(value), left(nullptr), right(nullptr) {}
 };
 
-Queue queue;
-
-void enqueue(node *n) { queue.t[queue.rear++] = n; }
-
-node *dequeue() { return (queue.t[queue.front++]); }
+class BinaryTree {
+public:
+    std::unique_ptr<Node> root; // Root of the binary tree
 
-void Insert(node *n, int x) {
-    if (x < n->val) {
-        if (n->left == NULL) {
-            node *temp = new node;
-            temp->val = x;
-            temp->left = NULL;
-            temp->right = NULL;
-            n->left = temp;
+    // Insert a value into the tree
+    void insert(int x) {
+        if (!root) {
+            root = std::make_unique<Node>(x); // Create root if it doesn't exist
         } else {
-            Insert(n->left, x);
+            insertHelper(root.get(), x); // Helper function for recursive insertion
         }
-    } else {
-        if (n->right == NULL) {
-            node *temp = new node;
-            temp->val = x;
-            temp->left = NULL;
-            temp->right = NULL;
-            n->right = temp;
-        } else {
-            Insert(n->right, x);
+    }
+
+    // Remove a value from the tree
+    void remove(int x) {
+        removeHelper(root, x); // Helper function to manage removal
+    }
+
+    // Breadth-first traversal of the tree
+    void breadthFirstTraversal() const {
+        if (!root) return;
+        std::queue<Node*> q; // Using STL queue for level-order traversal
+        q.push(root.get());
+        while (!q.empty()) {
+            Node* current = q.front();
+            q.pop();
+            std::cout << current->val << "  "; // Print the current node's value
+            if (current->left) q.push(current->left.get());
+            if (current->right) q.push(current->right.get());
         }
     }
-}
 
-int findMaxInLeftST(node *n) {
-    while (n->right != NULL) {
-        n = n->right;
+    // Preorder traversal
+    void preOrderTraversal() const {
+        preOrderHelper(root.get());
     }
-    return n->val;
-}
 
-void Remove(node *p, node *n, int x) {
-    if (n->val == x) {
-        if (n->right == NULL && n->left == NULL) {
-            if (x < p->val) {
-                p->right = NULL;
-            } else {
-                p->left = NULL;
-            }
-        } else if (n->right == NULL) {
-            if (x < p->val) {
-                p->right = n->left;
+    // Inorder traversal
+    void inOrderTraversal() const {
+        inOrderHelper(root.get());
+    }
+
+    // Postorder traversal
+    void postOrderTraversal() const {
+        postOrderHelper(root.get());
+    }
+
+private:
+    // Helper function for insertion
+    void insertHelper(Node* node, int x) {
+        if (x < node->val) {
+            if (!node->left) {
+                node->left = std::make_unique<Node>(x); // Create left child if it doesn't exist
             } else {
-                p->left = n->left;
+                insertHelper(node->left.get(), x); // Recur to the left
             }
-        } else if (n->left == NULL) {
-            if (x < p->val) {
-                p->right = n->right;
+        } else {
+            if (!node->right) {
+                node->right = std::make_unique<Node>(x); // Create right child if it doesn't exist
             } else {
-                p->left = n->right;
+                insertHelper(node->right.get(), x); // Recur to the right
             }
-        } else {
-            int y = findMaxInLeftST(n->left);
-            n->val = y;
-            Remove(n, n->right, y);
         }
-    } else if (x < n->val) {
-        Remove(n, n->left, x);
-    } else {
-        Remove(n, n->right, x);
     }
-}
 
-void BFT(node *n) {
-    if (n != NULL) {
-        std::cout << n->val << "  ";
-        enqueue(n->left);
-        enqueue(n->right);
-        BFT(dequeue());
+    // Helper function to find the maximum value in the left subtree
+    Node* findMaxInLeft(Node* node) {
+        while (node->right) {
+            node = node->right.get();
+        }
+        return node;
     }
-}
 
-void Pre(node *n) {
-    if (n != NULL) {
-        std::cout << n->val << "  ";
-        Pre(n->left);
-        Pre(n->right);
+    // Helper function for removing a node
+    Node* removeHelper(std::unique_ptr<Node>& node, int x) {
+        if (!node) return nullptr; // Base case: node not found
+
+        if (x < node->val) {
+            node->left = removeHelper(node->left, x); // Recur left
+        } else if (x > node->val) {
+            node->right = removeHelper(node->right, x); // Recur right
+        } else {
+            // Node found: handle three cases
+            if (!node->left) {
+                return std::move(node->right); // No left child
+            } else if (!node->right) {
+                return std::move(node->left); // No right child
+            } else {
+                // Node with two children: replace with max value from left subtree
+                int maxVal = findMaxInLeft(node->left.get())->val;
+                node->val = maxVal; // Replace value
+                node->left = removeHelper(node->left, maxVal); // Remove the max value
+            }
+        }
+        return std::move(node); // Return updated node
     }
-}
 
-void In(node *n) {
-    if (n != NULL) {
-        In(n->left);
-        std::cout << n->val << "  ";
-        In(n->right);
+    // Preorder traversal helper
+    void preOrderHelper(Node* node) const {
+        if (node) {
+            std::cout << node->val << "  "; // Visit node
+            preOrderHelper(node->left.get()); // Recur left
+            preOrderHelper(node->right.get()); // Recur right
+        }
     }
-}
 
-void Post(node *n) {
-    if (n != NULL) {
-        Post(n->left);
-        Post(n->right);
-        std::cout << n->val << "  ";
+    // Inorder traversal helper
+    void inOrderHelper(Node* node) const {
+        if (node) {
+            inOrderHelper(node->left.get()); // Recur left
+            std::cout << node->val << "  "; // Visit node
+            inOrderHelper(node->right.get()); // Recur right
+        }
     }
-}
+
+    // Postorder traversal helper
+    void postOrderHelper(Node* node) const {
+        if (node) {
+            postOrderHelper(node->left.get()); // Recur left
+            postOrderHelper(node->right.get()); // Recur right
+            std::cout << node->val << "  "; // Visit node
+        }
+    }
+};
 
 int main() {
-    queue.front = 0;
-    queue.rear = 0;
+    BinaryTree tree;
     int value;
-    int ch;
-    node *root = new node;
-    std::cout << "\nEnter the value of root node :";
+    std::cout << "\nEnter the value of root node: ";
     std::cin >> value;
-    root->val = value;
-    root->left = NULL;
-    root->right = NULL;
+    tree.insert(value); // Insert the root value
+
+    int choice;
     do {
         std::cout << "\n1. Insert"
                   << "\n2. Delete"
                   << "\n3. Breadth First"
                   << "\n4. Preorder Depth First"
                   << "\n5. Inorder Depth First"
-                  << "\n6. Postorder Depth First";
+                  << "\n6. Postorder Depth First"
+                  << "\n0. Exit"
+                  << "\nEnter Your Choice: ";
+        std::cin >> choice;
 
-        std::cout << "\nEnter Your Choice : ";
-        std::cin >> ch;
         int x;
-        switch (ch) {
+        switch (choice) {
         case 1:
-            std::cout << "\nEnter the value to be Inserted : ";
+            std::cout << "\nEnter the value to be Inserted: ";
             std::cin >> x;
-            Insert(root, x);
+            tree.insert(x); // Insert value
             break;
         case 2:
-            std::cout << "\nEnter the value to be Deleted : ";
+            std::cout << "\nEnter the value to be Deleted: ";
             std::cin >> x;
-            Remove(root, root, x);
+            tree.remove(x); // Remove value
             break;
         case 3:
-            BFT(root);
+            tree.breadthFirstTraversal(); // Perform breadth-first traversal
             break;
         case 4:
-            Pre(root);
+            tree.preOrderTraversal(); // Perform preorder traversal
             break;
         case 5:
-            In(root);
+            tree.inOrderTraversal(); // Perform inorder traversal
             break;
         case 6:
-            Post(root);
+            tree.postOrderTraversal(); // Perform postorder traversal
             break;
         }
-    } while (ch != 0);
+    } while (choice != 0); // Exit loop on choice 0
 
     return 0;
 }