Create 652-find-duplicate-subtrees.js

Author: everthis

652-find-duplicate-subtrees.js

@@ -0,0 +1,27 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {TreeNode[]}
+ */
+const findDuplicateSubtrees = function (root) {
+  const obj = {},
+    res = []
+  preOrder(root, obj, res)
+  return res
+}
+
+function preOrder(root, map, res) {
+  if (root === null) return '#'
+  const str =
+    root.val + preOrder(root.left, map, res) + preOrder(root.right, map, res)
+  if (!map[str]) map[str] = 0
+  map[str]++
+  if (map[str] === 2) res.push(root)
+  return str
+}