feat: add python and java solutions to leetcode problem: No.0257

See https://leetcode-cn.com/problems/binary-tree-paths/

Author: yanglbme

README.md

@@ -92,6 +92,7 @@
 1. [二叉树的层次遍历 II](/solution/0100-0199/0107.Binary%20Tree%20Level%20Order%20Traversal%20II/README.md)
 1. [二叉树的最大深度](/solution/0100-0199/0104.Maximum%20Depth%20of%20Binary%20Tree/README.md)
 1. [二叉树的最小深度](/solution/0100-0199/0111.Minimum%20Depth%20of%20Binary%20Tree/README.md)
+1. [二叉树的所有路径](/solution/0200-0299/0257.Binary%20Tree%20Paths/README.md)
 1. [路径总和](/solution/0100-0199/0112.Path%20Sum/README.md)
 1. [路径总和 II](/solution/0100-0199/0113.Path%20Sum%20II/README.md)
 1. [从前序与中序遍历序列构造二叉树](/solution/0100-0199/0105.Construct%20Binary%20Tree%20from%20Preorder%20and%20Inorder%20Traversal/README.md)

README_EN.md

@@ -89,6 +89,7 @@ Complete solutions to [LeetCode](https://leetcode-cn.com/problemset/all/), [LCOF
 1. [Binary Tree Level Order Traversal II](/solution/0100-0199/0107.Binary%20Tree%20Level%20Order%20Traversal%20II/README_EN.md)
 1. [Maximum Depth of Binary Tree](/solution/0100-0199/0104.Maximum%20Depth%20of%20Binary%20Tree/README_EN.md)
 1. [Minimum Depth of Binary Tree](/solution/0100-0199/0111.Minimum%20Depth%20of%20Binary%20Tree/README_EN.md)
+1. [Binary Tree Paths](/solution/0200-0299/0257.Binary%20Tree%20Paths/README_EN.md)
 1. [Path Sum](/solution/0100-0199/0112.Path%20Sum/README_EN.md)
 1. [Path Sum II](/solution/0100-0199/0113.Path%20Sum%20II/README_EN.md)
 1. [Construct Binary Tree from Preorder and Inorder Traversal](/solution/0100-0199/0105.Construct%20Binary%20Tree%20from%20Preorder%20and%20Inorder%20Traversal/README_EN.md)

solution/0200-0299/0257.Binary Tree Paths/README.md

@@ -27,22 +27,76 @@
 
 <!-- 这里可写通用的实现逻辑 -->
 
+深度优先搜索+路径记录。
+
 <!-- tabs:start -->
 
 ### **Python3**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```python
-
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def binaryTreePaths(self, root: TreeNode) -> List[str]:
+        def dfs(root):
+            if root is None:
+                return
+            path.append(str(root.val))
+            if root.left is None and root.right is None:
+                res.append("->".join(path))
+            dfs(root.left)
+            dfs(root.right)
+            path.pop()
+        res = []
+        path = []
+        dfs(root)
+        return res
 ```
 
 ### **Java**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```java
-
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    private List<String> res;
+    private List<String> path;
+
+    public List<String> binaryTreePaths(TreeNode root) {
+        if (root == null) return Collections.emptyList();
+        res = new ArrayList<>();
+        path = new ArrayList<>();
+        dfs(root);
+        return res;
+    }
+
+    private void dfs(TreeNode root) {
+        if (root == null) return;
+        path.add(String.valueOf(root.val));
+        if (root.left == null && root.right == null) {
+            res.add(String.join("->", path));
+        }
+        dfs(root.left);
+        dfs(root.right);
+        path.remove(path.size() - 1);
+    }
+}
 ```
 
 ### **...**

solution/0200-0299/0257.Binary Tree Paths/README_EN.md

@@ -43,13 +43,65 @@
 ### **Python3**
 
 ```python
-
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def binaryTreePaths(self, root: TreeNode) -> List[str]:
+        def dfs(root):
+            if root is None:
+                return
+            path.append(str(root.val))
+            if root.left is None and root.right is None:
+                res.append("->".join(path))
+            dfs(root.left)
+            dfs(root.right)
+            path.pop()
+        res = []
+        path = []
+        dfs(root)
+        return res
 ```
 
 ### **Java**
 
 ```java
-
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    private List<String> res;
+    private List<String> path;
+
+    public List<String> binaryTreePaths(TreeNode root) {
+        if (root == null) return Collections.emptyList();
+        res = new ArrayList<>();
+        path = new ArrayList<>();
+        dfs(root);
+        return res;
+    }
+
+    private void dfs(TreeNode root) {
+        if (root == null) return;
+        path.add(String.valueOf(root.val));
+        if (root.left == null && root.right == null) {
+            res.add(String.join("->", path));
+        }
+        dfs(root.left);
+        dfs(root.right);
+        path.remove(path.size() - 1);
+    }
+}
 ```
 
 ### **...**

solution/0200-0299/0257.Binary Tree Paths/Solution.java

@@ -1,20 +1,32 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
 class Solution {
+    private List<String> res;
+    private List<String> path;
+
     public List<String> binaryTreePaths(TreeNode root) {
-        List<String> res = new ArrayList<>();
-        solution(root, "", res);
+        if (root == null) return Collections.emptyList();
+        res = new ArrayList<>();
+        path = new ArrayList<>();
+        dfs(root);
         return res;
     }
 
-    private void solution(TreeNode root, String path, List<String> res) {
-        if (root != null) {
-            path += root.val;
-            if (root.left == null && root.right == null) {
-                res.add(path);
-            } else {
-                path += "->";
-                solution(root.left, path, res);
-                solution(root.right, path, res);
-            }
+    private void dfs(TreeNode root) {
+        if (root == null) return;
+        path.add(String.valueOf(root.val));
+        if (root.left == null && root.right == null) {
+            res.add(String.join("->", path));
         }
+        dfs(root.left);
+        dfs(root.right);
+        path.remove(path.size() - 1);
     }
-}
+}

solution/0200-0299/0257.Binary Tree Paths/Solution.py

@@ -0,0 +1,22 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def binaryTreePaths(self, root: TreeNode) -> List[str]:
+        def dfs(root):
+            if root is None:
+                return
+            path.append(str(root.val))
+            if root.left is None and root.right is None:
+                res.append("->".join(path))
+            dfs(root.left)
+            dfs(root.right)
+            path.pop()
+        res = []
+        path = []
+        dfs(root)
+        return res