granmoe · January 24, 2020 17:14 · Jan 24, 2020
diff --git a/answer.js b/answer.js
@@ -0,0 +1,46 @@
+/**
+ * Given an array of Person objects, returns the root PersonTreeNode (the CEO).
+ * @param {Person[]} employees - An array of Person objects representing all the employees of the company.
+ * @returns {PersonTreeNode} The CEO of the organization.
+ */
+function generateTree(employees) {
+  let ceo = null
+
+  const visitedById = new Map()
+  const visitedByManagerId = new Map()
+
+  for (const employee of employees) {
+    const node = new PersonTreeNode(employee)
+    visitedById.set(employee.id, node)
+
+    // Add any direct reports we've already visited for this manager
+    const visitedDirectReports = visitedByManagerId.get(employee.id)
+    if (Array.isArray(visitedDirectReports)) {
+      node.directReports.push(...visitedDirectReports)
+    }
+
+    // Check if this is the CEO and skip the remaining logic in the loop if so
+    if (employee.manager === null) {
+      ceo = node
+      continue
+    }
+
+    const managerNode = visitedById.get(employee.manager.id)
+    if (managerNode) {
+      // Add our node to its manager's direct reports (if manager visited)
+      managerNode.directReports.push(node)
+    } else {
+      // Otherwise add node to map to be added to the manager's direct reports once we visit the manager
+      const visitedDirectReportsForManager = visitedByManagerId.get(
+        employee.manager.id,
+      )
+      if (Array.isArray(visitedDirectReportsForManager)) {
+        visitedDirectReportsForManager.push(node)
+      } else {
+        visitedByManagerId.set(employee.manager.id, [node])
+      }
+    }
+  }
+
+  return ceo
+}
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