solve problem Sum Root To Leaf Numbers

Author: P-ppc

README.md

@@ -283,6 +283,7 @@ All solutions will be accepted!
 |200|[Number Of Islands](https://leetcode-cn.com/problems/number-of-islands/description/)|[java/py/js](./algorithms/NumberOfIslands)|Medium|
 |223|[Rectangle Area](https://leetcode-cn.com/problems/rectangle-area/description/)|[java/py/js](./algorithms/RectangleArea)|Medium|
 |419|[Battleships In A Board](https://leetcode-cn.com/problems/battleships-in-a-board/description/)|[java/py/js](./algorithms/BattleshipsInABoard)|Medium|
+|129|[Sum Root To Leaf Numbers](https://leetcode-cn.com/problems/sum-root-to-leaf-numbers/description/)|[java/py/js](./algorithms/SumRootToLeafNumbers)|Medium|
 
 # Database
 |#|Title|Solution|Difficulty|

algorithms/SumRootToLeafNumbers/README.md

@@ -0,0 +1,2 @@
+# Sum Root To Leaf Numbers
+This problem is easy to solve by DFS

algorithms/SumRootToLeafNumbers/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 int sumNumbers(TreeNode root) {
+        return root == null ? 0 : helper(root, 0);
+    }
+    
+    public int helper(TreeNode root, int prefix) {
+        int val = prefix * 10 + root.val;
+        if (root.left == null && root.right == null)
+            return val;
+        else
+            return (root.left == null ? 0 : helper(root.left, val)) +
+                   (root.right == null ? 0 : helper(root.right, val));
+    }
+}

algorithms/SumRootToLeafNumbers/solution.js

@@ -0,0 +1,21 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var sumNumbers = function(root) {
+    return root ? helper(root, 0) : 0
+};
+
+var helper = function (root, prefix) {
+    if (!root.left && !root.right)
+        return prefix * 10 + root.val
+    else
+        return (root.left ? helper(root.left, prefix * 10 + root.val) : 0) + (root.right ? helper(root.right, prefix * 10 + root.val) : 0)
+}

algorithms/SumRootToLeafNumbers/solution.py

@@ -0,0 +1,20 @@
+# 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 sumNumbers(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        return self.helper(root, 0) if root else 0
+    
+    def helper(self, root, prefix):
+        if not root.left and not root.right:
+            return prefix * 10 + root.val
+        else:
+            return (self.helper(root.left, prefix * 10 + root.val) if root.left else 0) + (self.helper(root.right, prefix * 10 + root.val) if root.right else 0)