Create lowest_common_ancestor.cpp

lowest_common_ancestor.cpp

@@ -0,0 +1,45 @@
+#include <iostream>
+
+struct TreeNode {
+    int val;
+    TreeNode* left;
+    TreeNode* right;
+    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+};
+
+TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
+    if (!root) return nullptr;
+
+    if (p->val < root->val && q->val < root->val) {
+        return lowestCommonAncestor(root->left, p, q);
+    } else if (p->val > root->val && q->val > root->val) {
+        return lowestCommonAncestor(root->right, p, q);
+    } else {
+        return root;
+    }
+}
+
+int main() {
+    // Create a BST
+    TreeNode* root = new TreeNode(20);
+    root->left = new TreeNode(10);
+    root->right = new TreeNode(30);
+    root->left->left = new TreeNode(5);
+    root->left->right = new TreeNode(15);
+    root->right->left = new TreeNode(25);
+    root->right->right = new TreeNode(35);
+
+    TreeNode* p = root->left->left;  // Node with value 5
+    TreeNode* q = root->left->right; // Node with value 15
+
+    TreeNode* lca = lowestCommonAncestor(root, p, q);
+
+    if (lca) {
+        std::cout << "Lowest Common Ancestor: " << lca->val << std::endl;
+    } else {
+        std::cout << "No common ancestor found." << std::endl;
+    }
+
+    // Clean up memory (not shown for brevity)
+    return 0;
+}