add: 220419 [cpp]

cpp/2204/220419.cpp

@@ -0,0 +1,50 @@
+#include <functional>
+#include <cstdio>
+
+struct TreeNode {
+	int val;
+	TreeNode* left;
+	TreeNode* right;
+
+	explicit TreeNode(int x = 0, TreeNode* l = nullptr, TreeNode* r = nullptr) : val(x), left(l), right(r) {}
+};
+
+/**
+ * 99. Recover Binary Search Tree
+ * You are given the root of a binary search tree (BST), where the values of exactly two nodes of the tree were swapped by mistake. Recover the tree without changing its structure.
+ */
+
+class Solution {
+public:
+	static void recoverTree(TreeNode* root) {
+		TreeNode* prev = nullptr, * x1 = nullptr, * x2 = nullptr;
+		std::function<bool(TreeNode*)> traverse = [&](TreeNode* r) {
+			if (!r)
+				return false;
+			if (r->left && traverse(r->left))
+				return true;
+
+			// Check if prevPrev < r
+			if (prev && prev->val >= r->val) {
+				x1 = r;
+				if (!x2)
+					x2 = prev;
+				else
+					return true;
+			}
+			prev = r;
+
+			if (r->right)
+				return traverse(r->right);
+			return false;
+		};
+		traverse(root);
+		std::swap(x1->val, x2->val);
+	}
+};
+
+int main() {
+	auto* root = new TreeNode(1, new TreeNode(3, nullptr, new TreeNode(2)));
+	Solution::recoverTree(root);
+	return 0;
+}

cpp/2204/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2204)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2204 220419-CN.cpp)
+ADD_EXECUTABLE(2204 220419.cpp)