Add solution #671

Author: JoshCrozier

README.md

@@ -504,6 +504,7 @@
 668|[Kth Smallest Number in Multiplication Table](./0668-kth-smallest-number-in-multiplication-table.js)|Hard|
 669|[Trim a Binary Search Tree](./0669-trim-a-binary-search-tree.js)|Medium|
 670|[Maximum Swap](./0670-maximum-swap.js)|Medium|
+671|[Second Minimum Node In a Binary Tree](./0671-second-minimum-node-in-a-binary-tree.js)|Easy|
 680|[Valid Palindrome II](./0680-valid-palindrome-ii.js)|Easy|
 684|[Redundant Connection](./0684-redundant-connection.js)|Medium|
 686|[Repeated String Match](./0686-repeated-string-match.js)|Easy|

solutions/0671-second-minimum-node-in-a-binary-tree.js

@@ -0,0 +1,36 @@
+/**
+ * 671. Second Minimum Node In a Binary Tree
+ * https://leetcode.com/problems/second-minimum-node-in-a-binary-tree/
+ * Difficulty: Easy
+ *
+ * Given a non-empty special binary tree consisting of nodes with the non-negative value,
+ * where each node in this tree has exactly two or zero sub-node. If the node has two
+ * sub-nodes, then this node's value is the smaller value among its two sub-nodes. More
+ * formally, the property root.val = min(root.left.val, root.right.val) always holds.
+ *
+ * Given such a binary tree, you need to output the second minimum value in the set made
+ * of all the nodes' value in the whole tree.
+ *
+ * If no such second minimum value exists, output -1 instead.
+ */
+
+/**
+ * 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 findSecondMinimumValue = function(root) {
+  return root ? (n => n === Infinity ? -1 : n)(traverse(root, root.val)) : -1;
+  function traverse(node, min) {
+    if (!node) return Infinity;
+    if (node.val > min) return node.val;
+    return Math.min(traverse(node.left, min), traverse(node.right, min));
+  }
+};