1 files changed, 60 insertions, 0 deletions
diff --git a/works/solutions/cpp/865.cpp b/works/solutions/cpp/865.cpp
new file mode 100644
index 0000000..8981a02
--- /dev/null
+++ b/works/solutions/cpp/865.cpp
@@ -0,0 +1,60 @@
+struct TreeNode
+{
+    int val;
+    TreeNode *left;
+    TreeNode *right;
+    TreeNode() : val(0), left(nullptr), right(nullptr) {}
+    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+};
+
+#include <unordered_set>
+
+class Solution
+{
+public:
+    int max_depth = -1;
+    std::unordered_set<TreeNode *> deepest_nodes;
+
+    void record_depth(TreeNode *root, int depth)
+    {
+        if (depth > max_depth)
+        {
+            max_depth = depth;
+            deepest_nodes.clear();
+        }
+
+        if (depth == max_depth)
+            deepest_nodes.insert(root);
+
+        if (root->left != nullptr)
+            record_depth(root->left, depth + 1);
+        if (root->right != nullptr)
+            record_depth(root->right, depth + 1);
+    }
+
+    TreeNode *find_common_ancestor(TreeNode *root)
+    {
+        if (root == nullptr)
+            return nullptr;
+        if (deepest_nodes.find(root) != deepest_nodes.cend())
+            return root;
+
+        auto left = find_common_ancestor(root->left);
+        auto right = find_common_ancestor(root->right);
+
+        if (left != nullptr && right != nullptr)
+            return root;
+        if (left != nullptr)
+            return left;
+        if (right != nullptr)
+            return right;
+        return nullptr;
+    }
+
+    TreeNode *subtreeWithAllDeepest(TreeNode *root)
+    {
+        record_depth(root, 0);
+        return find_common_ancestor(root);
+    }
+};