add: 230228

cpp/2302/230228.cpp

@@ -0,0 +1,56 @@
+#include <vector>
+#include <unordered_map>
+#include <string>
+
+struct TreeNode {
+	int val;
+	TreeNode* left;
+	TreeNode* right;
+
+	explicit TreeNode(int x = 0, TreeNode* left = nullptr, TreeNode* right = nullptr) : val(x), left(left), right(right) {}
+};
+
+/**
+ * 652. Find Duplicate Subtrees
+ *
+ * Given the root of a binary tree, return all duplicate subtrees.
+ * For each kind of duplicate subtrees, you only need to return the root node of any one of them.
+ * Two trees are duplicate if they have the same structure with the same node values.
+ */
+
+class Solution {
+private:
+	std::unordered_map<std::string, TreeNode*> strToNode;
+	std::unordered_map<std::string, int> strCnt;
+
+	// Pre-order
+	std::string toStr(TreeNode* r) {
+		if (!r)
+			return "";
+		auto ret = std::to_string(r->val)
+			.append("(")
+			.append(toStr(r->left))
+			.append(")(")
+			.append(toStr(r->right))
+			.append(")");
+		strToNode[ret] = r;
+		++strCnt[ret];
+		return ret;
+	}
+
+public:
+	std::vector<TreeNode*> findDuplicateSubtrees(TreeNode* r) {
+		toStr(r);
+		std::vector<TreeNode*> ret;
+		for (const auto& [str, c] : strCnt) {
+			if (c <= 1)
+				continue;
+			ret.push_back(strToNode[str]);
+		}
+		return ret;
+	}
+};
+
+int main() {
+	return 0;
+}

cpp/2302/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2302)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2302 230228-CN.cpp)
+ADD_EXECUTABLE(2302 230228.cpp)