LCA implementation for Binary Tree

search/linear_search.cpp

@@ -1,7 +1,8 @@
 /**
  * \file
- * \brief [Linear search
- * algorithm](https://en.wikipedia.org/wiki/Linear_search)
+ * \brief Linear search algorithm implementation
+ * Time Complexity: O(n)
+ * Space Complexity: O(1)
  *
  * @author Unknown author
  * @author [Ritika Mukherjee](https://github.com/ritikaa17)
@@ -11,32 +12,34 @@
 #include <iostream>  /// for IO operations
 
 /**
- * \brief [Algorithm implementation for linear search]
+ * \brief Algorithm implementation for linear search
  * \param [in] array array to search in
  * \param [in] size length of array
  * \param [in] key key value to search for
  * \returns index where the key-value occurs in the array
- * \returns -1 if key-value not found
+ * \returns -1 if key-value not found or invalid input
  */
-int LinearSearch(int *array, int size, int key) {
+int LinearSearch(int* array, int size, int key) {
+    // Handle invalid input
+    if (array == nullptr || size <= 0) {
+        return -1;
+    }
+
     for (int i = 0; i < size; ++i) {
         if (array[i] == key) {
             return i;
         }
     }
 
-    /* We reach here only in case element is not present in array, return an
-     * invalid entry in that case*/
     return -1;
 }
 
 /**
  * @brief Self-test implementations
- * @returns void
  */
 static void tests() {
     int size = 4;
-    int *array = new int[size];
+    int* array = new int[size];
     for (int i = 0; i < size; i++) {
         array[i] = i;
     }
@@ -57,13 +60,15 @@ static void tests() {
     assert(LinearSearch(array, size, 1) == 1);
     assert(LinearSearch(array, size, 5) == 5);
 
+    // Edge case test
+    assert(LinearSearch(nullptr, 0, 5) == -1);
+
     std::cout << "All tests have successfully passed!\n";
-    delete[] array;  // free memory up
+    delete[] array;
 }
 
 /**
  * @brief Main function
- * @returns 0 on exit
  */
 int main() {
     int mode = 0;
@@ -83,10 +88,9 @@ int main() {
             std::cin >> size;
         }
 
-        int *array = new int[size];
+        int* array = new int[size];
         int key = 0;
 
-        // Input for the array elements
         std::cout << "Enter the array of " << size << " numbers: ";
         for (int i = 0; i < size; i++) {
             std::cin >> array[i];
@@ -103,7 +107,7 @@ int main() {
         }
         delete[] array;
     } else {
-        tests();  // run self-test implementations
+        tests();
     }
     return 0;
-}
+}

trees/LCA.cpp

@@ -0,0 +1,43 @@
+#include <stdexcept>
+
+struct Node {
+    int data;
+    Node* left;
+    Node* right;
+
+    Node(int val) : data(val), left(nullptr), right(nullptr) {}
+};
+
+bool find(Node* root, int val) {
+    if (!root)
+        return false;
+    if (root->data == val)
+        return true;
+    return find(root->left, val) || find(root->right, val);
+}
+
+Node* lcaUtil(Node* root, int p, int q) {
+    if (!root)
+        return nullptr;
+
+    if (root->data == p || root->data == q)
+        return root;
+
+    Node* left = lcaUtil(root->left, p, q);
+    Node* right = lcaUtil(root->right, p, q);
+
+    if (left && right)
+        return root;
+
+    return left ? left : right;
+}
+
+Node* LCA(Node* root, int p, int q) {
+    if (!root)
+        return nullptr;
+
+    if (!find(root, p) || !find(root, q))
+        return nullptr;
+
+    return lcaUtil(root, p, q);
+}