Add solution #617

Author: JoshCrozier

solutions/0617-merge-two-binary-trees.js

@@ -0,0 +1,38 @@
+/**
+ * 617. Merge Two Binary Trees
+ * https://leetcode.com/problems/merge-two-binary-trees/
+ * Difficulty: Easy
+ *
+ * Given two binary trees and imagine that when you put one
+ * of them to cover the other, some nodes of the two trees
+ * are overlapped while the others are not.
+ *
+ * You need to merge them into a new binary tree.
+ * The merge rule is that if two nodes overlap, then sum
+ * node values up as the new value of the merged node.
+ * Otherwise, the NOT null node will be used as the
+ * node of new tree.
+ */
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} t1
+ * @param {TreeNode} t2
+ * @return {TreeNode}
+ */
+var mergeTrees = function(t1, t2) {
+  if (!t1) return t2;
+  if (!t2) return t1;
+
+  t1.val += t2.val;
+  t1.left = mergeTrees(t1.left, t2.left);
+  t1.right = mergeTrees(t1.right, t2.right);
+
+  return t1;
+};