solve problem Binary Tree Pruning

Author: P-ppc

README.md

@@ -265,6 +265,7 @@ All solutions will be accepted!
 |885|[Spiral Matrix III](https://leetcode-cn.com/problems/spiral-matrix-iii/description/)|[java/py/js](./algorithms/SpiralMatrixIII)|Medium|
 |19|[Remove Nth Node From End Of List](https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/description/)|[java/py/js](./algorithms/RemoveNthNodeFromEndOfList)|Medium|
 |526|[Beautiful Arrangement](https://leetcode-cn.com/problems/beautiful-arrangement/description/)|[java/py/js](./algorithms/BeautifulArrangement)|Medium|
+|814|[Binary Tree Pruning](https://leetcode-cn.com/problems/binary-tree-pruning/description/)|[java/py/js](./algorithms/BinaryTreePruning)|Medium|
 
 # Database
 |#|Title|Solution|Difficulty|

algorithms/BinaryTreePruning/README.md

@@ -0,0 +1,2 @@
+# Binary Tree Pruning
+We can solve this problem by recursive

algorithms/BinaryTreePruning/Solution.java

@@ -0,0 +1,23 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public TreeNode pruneTree(TreeNode root) {
+        root.left = root.left != null ? helper(root.left) : null;
+        root.right = root.right != null ? helper(root.right) : null;
+        return root;
+    }
+    
+    public TreeNode helper(TreeNode root) {
+        root.left = root.left != null ? helper(root.left) : null;
+        root.right = root.right != null ? helper(root.right) : null;
+        
+        return (root.left != null || root.right != null || root.val == 1) ? root : null;
+    }
+}

algorithms/BinaryTreePruning/solution.js

@@ -0,0 +1,23 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {TreeNode}
+ */
+var pruneTree = function(root) {
+    root.left = root.left ? helper(root.left) : null
+    root.right = root.right ? helper(root.right) : null
+    return root
+};
+
+var helper = function(root) {
+    root.left = root.left ? helper(root.left) : null
+    root.right = root.right ? helper(root.right) : null
+    
+    return (root.left || root.right || root.val == 1) ? root : null
+}

algorithms/BinaryTreePruning/solution.py

@@ -0,0 +1,24 @@
+# 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 pruneTree(self, root):
+        """
+        :type root: TreeNode
+        :rtype: TreeNode
+        """
+        self.helper(root)
+        return root
+    
+    def helper(self, root):
+        left_flag = False if not root.left else self.helper(root.left)
+        right_flag = False if not root.right else self.helper(root.right)
+        if not left_flag:
+            root.left = None
+        if not right_flag:
+            root.right = None
+        return root.val == 1 or left_flag or right_flag