add: 220415 [cpp]

cpp/2204/220415.cpp

@@ -0,0 +1,29 @@
+#include <iostream>
+
+struct TreeNode {
+	int val;
+	TreeNode* left;
+	TreeNode* right;
+	explicit TreeNode(int x, TreeNode* left = nullptr, TreeNode* right = nullptr) : val(x), left(left), right(right) {}
+};
+
+/**
+ * 669. Trim a Binary Search Tree
+ * Given the root of a binary search tree and the lowest and highest boundaries as low and high, trim the tree so that all its elements lies in [low, high]. Trimming the tree should not change the relative structure of the elements that will remain in the tree (i.e., any node's descendant should remain a descendant). It can be proven that there is a unique answer.
+ * Return the root of the trimmed binary search tree. Note that the root may change depending on the given bounds.
+ */
+
+class Solution {
+public:
+	static TreeNode* trimBST(TreeNode* root, int low, int high) {
+		if (!root)
+			return nullptr;
+		if (root->val < low)
+			return trimBST(root->right, low, high);
+		if (high < root->val)
+			return trimBST(root->left, low, high);
+		root->left = trimBST(root->left, low, high);
+		root->right = trimBST(root->right, low, high);
+		return root;
+	}
+};