solve problem Trim A Binary Search Tree

Author: P-ppc

README.md

@@ -64,6 +64,7 @@ All solutions will be accepted!
 |257|[Binary Tree Paths](https://leetcode-cn.com/problems/binary-tree-paths/description/)|[java/py/js](./algorithms/BinaryTreePaths)|Easy|
 |496|[Next Greater Element I](https://leetcode-cn.com/problems/next-greater-element-i/description/)|[java/py/js](./algorithms/NextGeraterElementI)|Easy|
 |766|[Toeplitz Matrix](https://leetcode-cn.com/problems/toeplitz-matrix/description/)|[java/py/js](./algorithms/ToeplitzMatrix)|Easy|
+|669|[Trim A Binary Search Tree](https://leetcode-cn.com/problems/trim-a-binary-search-tree/description/)|[java/py/js](./algorithms/TrimABinarySearchTree)|Easy|
 
 # Database
 |#|Title|Solution|Difficulty|

algorithms/TrimABinarySearchTree/README.md

@@ -0,0 +1,2 @@
+# Trim A Binary Search Tree
+This problem is easy to solve by recursion

algorithms/TrimABinarySearchTree/Solution.java

@@ -0,0 +1,24 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public TreeNode trimBST(TreeNode root, int L, int R) {
+        if (root == null) {
+            return null;
+        } else if (root.val > R) {
+            return trimBST(root.left, L, R);
+        } else if (root.val < L) {
+            return trimBST(root.right, L, R);
+        } else {
+            root.left = trimBST(root.left, L, R);
+            root.right = trimBST(root.right, L, R);
+            return root;
+        }
+    }
+}

algorithms/TrimABinarySearchTree/solution.js

@@ -0,0 +1,26 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {number} L
+ * @param {number} R
+ * @return {TreeNode}
+ */
+var trimBST = function(root, L, R) {
+    if (root === null) {
+        return null
+    } else if (root.val > R) {
+        return trimBST(root.left, L, R)
+    } else if (root.val < L) {
+        return trimBST(root.right, L, R)
+    } else {
+        root.left = trimBST(root.left, L, R)
+        root.right = trimBST(root.right, L, R)
+        return root
+    }
+};

algorithms/TrimABinarySearchTree/solution.py

@@ -0,0 +1,25 @@
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def trimBST(self, root, L, R):
+        """
+        :type root: TreeNode
+        :type L: int
+        :type R: int
+        :rtype: TreeNode
+        """
+        if not root:
+            return None
+        elif root.val < L:
+            return self.trimBST(root.right, L, R)
+        elif root.val > R:
+            return self.trimBST(root.left, L, R)
+        else:
+            root.left = self.trimBST(root.left, L, R)
+            root.right = self.trimBST(root.right, L, R)
+            return root