s0236

include/s0236_lowest_common_ancestor_of_a_binary_tree.hpp

@@ -0,0 +1,11 @@
+#ifndef S0236_LOWEST_COMMON_ANCESTOR_OF_A_BINARY_TREE_HPP
+#define S0236_LOWEST_COMMON_ANCESTOR_OF_A_BINARY_TREE_HPP
+
+#include "structures.hpp"
+
+class S0236 {
+ public:
+  TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q);
+};
+
+#endif

src/s0236_lowest_common_ancestor_of_a_binary_tree.cpp

@@ -0,0 +1,17 @@
+#include "s0236_lowest_common_ancestor_of_a_binary_tree.hpp"
+
+TreeNode* S0236::lowestCommonAncestor(TreeNode* root, TreeNode* p,
+                                      TreeNode* q) {
+  if (root == nullptr || root == p || root == q) return root;
+  TreeNode* left = lowestCommonAncestor(root->left, p, q);
+  TreeNode* right = lowestCommonAncestor(root->right, p, q);
+  if (left != nullptr && right != nullptr) {
+    return root;
+  } else if (left != nullptr) {
+    return left;
+  } else if (right != nullptr) {
+    return right;
+  } else {
+    return nullptr;
+  }
+}