Add solution #129

Author: JoshCrozier

README.md

@@ -133,6 +133,7 @@
 125|[Valid Palindrome](./0125-valid-palindrome.js)|Easy|
 127|[Word Ladder](./0127-word-ladder.js)|Hard|
 128|[Longest Consecutive Sequence](./0128-longest-consecutive-sequence.js)|Medium|
+129|[Sum Root to Leaf Numbers](./0129-sum-root-to-leaf-numbers.js)|Medium|
 131|[Palindrome Partitioning](./0131-palindrome-partitioning.js)|Medium|
 133|[Clone Graph](./0133-clone-graph.js)|Medium|
 134|[Gas Station](./0134-gas-station.js)|Medium|

solutions/0129-sum-root-to-leaf-numbers.js

@@ -0,0 +1,43 @@
+/**
+ * 129. Sum Root to Leaf Numbers
+ * https://leetcode.com/problems/sum-root-to-leaf-numbers/
+ * Difficulty: Medium
+ *
+ * You are given the root of a binary tree containing digits from 0 to 9 only.
+ *
+ * Each root-to-leaf path in the tree represents a number.
+ *
+ * - For example, the root-to-leaf path 1 -> 2 -> 3 represents the number 123.
+ *
+ * Return the total sum of all root-to-leaf numbers. Test cases are generated
+ * so that the answer will fit in a 32-bit integer.
+ *
+ * A leaf node is a node with no children.
+ */
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var sumNumbers = function(root) {
+  function traverse(node, value) {
+    if (!node) {
+      return null;
+    }
+    value += node.val;
+    if (!node.left && !node.right) {
+      return Number(value);
+    }
+    return traverse(node.left, value) + traverse(node.right, value);
+  }
+
+  return traverse(root, '');
+};