From 837812e5994c7ae6ade285e103aed51931fb1adb Mon Sep 17 00:00:00 2001
From: Sainnhe Park <i@sainnhe.dev>
Date: Tue, 31 Jan 2023 16:08:05 +0800
Subject: [PATCH] s0236

---
 ..._lowest_common_ancestor_of_a_binary_tree.hpp | 11 +++++++++++
 ..._lowest_common_ancestor_of_a_binary_tree.cpp | 17 +++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 include/s0236_lowest_common_ancestor_of_a_binary_tree.hpp
 create mode 100644 src/s0236_lowest_common_ancestor_of_a_binary_tree.cpp

diff --git a/include/s0236_lowest_common_ancestor_of_a_binary_tree.hpp b/include/s0236_lowest_common_ancestor_of_a_binary_tree.hpp
new file mode 100644
index 0000000..3ec4f6a
--- /dev/null
+++ b/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
diff --git a/src/s0236_lowest_common_ancestor_of_a_binary_tree.cpp b/src/s0236_lowest_common_ancestor_of_a_binary_tree.cpp
new file mode 100644
index 0000000..734f3e9
--- /dev/null
+++ b/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;
+  }
+}