Added same tree solution

Author: nhistory

same-tree/nhistory.js

@@ -0,0 +1,24 @@
+/**
+ * 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} p
+ * @param {TreeNode} q
+ * @return {boolean}
+ */
+var isSameTree = function (p, q) {
+  // If p and q is null, return true
+  if (!p && !q) return true;
+  // Compare root and length between p and q
+  if (!p || !q || p.val !== q.val) return false;
+  // Execute recursive function to search each tree
+  return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
+};
+
+// TC: O(n)
+// SC: O(n)