Merge pull request #637 from Paila-Sahitya/add-treeTraversals

Added recursive inorder, preorder, and postorder tree traversals

Author: Karanjot786

CPP/data_structures/trees/treeTraversals.cpp

@@ -0,0 +1,88 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+/*
+Algorithm: Binary Tree Traversals (Inorder, Preorder, Postorder)
+
+Description:
+- Builds a Binary Search Tree (BST) using insertion.
+- Performs recursive traversals:
+     Inorder (Left → Root → Right)
+     Preorder (Root → Left → Right)
+     Postorder (Left → Right → Root)
+- Useful for processing hierarchical data, syntax trees, and expression evaluation.
+
+Time Complexity: O(n)
+Space Complexity: O(h), where h is tree height (O(log n) average, O(n) worst case)
+*/
+
+class TreeNode {
+public:
+    int data;
+    TreeNode* left;
+    TreeNode* right;
+
+    TreeNode(int val) {
+        data = val;
+        left = NULL;
+        right = NULL;
+    }
+};
+
+// Function to insert a node into the BST
+TreeNode* insert(TreeNode* root, int val) {
+
+    if (!root) return new TreeNode(val);
+    if (val < root->data) root->left = insert(root->left, val);
+    else root->right = insert(root->right, val);
+    return root;
+}
+
+// Inorder traversal (Left, Root, Right)
+void inorder(TreeNode* root) {
+    if (!root) return;
+    inorder(root->left);
+    cout << root->data << " ";
+    inorder(root->right);
+}
+
+//Preorder traversal (Root, Left, Right)
+void preorder(TreeNode* root){
+    if(!root) return;
+    cout<<root->data<<" ";
+    preorder(root->left);
+    preorder(root->right);
+}
+
+//Postorder traversal (Left, Right, Root)
+void postorder(TreeNode* root){
+    if(!root) return;
+    postorder(root->left);
+    postorder(root->right);
+    cout<<root->data<<" ";
+}
+
+
+int main() {
+    TreeNode* root = NULL;
+    int n, val;
+
+    cout << "Enter number of nodes: ";
+    cin >> n;
+
+    cout << "Enter values to insert into BST:";
+    for (int i = 0; i < n; i++) {
+        cin >> val;
+        root = insert(root, val);
+    }
+
+    cout << "\nInorder Traversal: ";
+    inorder(root);
+    cout << "\nPreorder Traversal: ";
+    preorder(root);
+    cout<<"\nPostorder Traversal: ";
+    postorder(root);
+    cout<<endl;
+
+    return 0;
+}