solves time needed to infrom all employees in java

Author: anishLearnsToCode

README.md

@@ -531,6 +531,7 @@
 | 1365 | [How Many Numbers Are Smaller Than Current Number](https://leetcode.com/problems/how-many-numbers-are-smaller-than-the-current-number)                    |                                                    [![Java](assets/java.png)](src/HowManyNumbersAreSmallerThanCurrentNumber.java)                                                    |                                                                                                                                   |
 | 1370 | [Increasing Decreasing String](https://leetcode.com/problems/increasing-decreasing-string)                                                                |                                                           [![Java](assets/java.png)](src/IncreasingDecreasingString.java)                                                            |                                                                                                                                   |
 | 1374 | [Generate A String With Characters That Have Odd Count](https://leetcode.com/problems/generate-a-string-with-characters-that-have-odd-counts)             |                                                 [![Java](assets/java.png)](src/GenerateAStringWithCharactersThatHaveOddCounts.java)                                                  |                                                                                                                                   |
+| 1376 | [Time Needed to Inform All Employees](https://leetcode.com/problems/time-needed-to-inform-all-employees)                                                  |                                                         [![Java](assets/java.png)](src/TimeNeededToInformAllEmployees.java)                                                          |                                                                                                                                   |
 | 1380 | [Lucky Numbers In A Matrix](https://leetcode.com/problems/lucky-numbers-in-a-matrix)                                                                      |                                                              [![Java](assets/java.png)](src/LuckyNumbersInAMatrix.java)                                                              |                                                                                                                                   |
 | 1385 | [Find The Distance Value Between 2 Arrays](https://leetcode.com/problems/find-the-distance-value-between-two-arrays)                                      |                                                      [![Java](assets/java.png)](src/FindTheDistanceValuesBetweenTwoArrays.java)                                                      |                                                                                                                                   |
 | 1389 | [Create Target Array in Given Order](https://leetcode.com/problems/create-target-array-in-the-given-order)                                                |                                                          [![Java](assets/java.png)](src/CreateTargetArrayInGivenOrder.java)                                                          |                                                                                                                                   |

src/TimeNeededToInformAllEmployees.java

@@ -0,0 +1,57 @@
+// https://leetcode.com/problems/time-needed-to-inform-all-employees
+// T: O(n)
+// S: O(n)
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class TimeNeededToInformAllEmployees {
+    private static final class TreeNode {
+        int val;
+        List<TreeNode> subordinates = new ArrayList<>();
+
+        TreeNode(int val) {
+            this.val = val;
+        }
+
+        private boolean hasSubordinates() {
+            return subordinates.size() > 0;
+        }
+
+        private void addSubordinate(TreeNode subordinate) {
+            this.subordinates.add(subordinate);
+        }
+    }
+
+    public int numOfMinutes(int n, int headID, int[] manager, int[] informTime) {
+        TreeNode company = createEmployeeGraph(headID, manager);
+        return timeNeededForInformationDispersal(company, informTime);
+    }
+
+    private int timeNeededForInformationDispersal(TreeNode root, int[] informTime) {
+        if (root == null || !root.hasSubordinates()) return 0;
+        int timeTaken = 0;
+        for (TreeNode subordinate : root.subordinates) {
+            timeTaken = Math.max(timeTaken, timeNeededForInformationDispersal(subordinate, informTime));
+        }
+        return timeTaken + informTime[root.val];
+    }
+
+    private TreeNode createEmployeeGraph(int headIndex, int[] managers) {
+        final TreeNode root = new TreeNode(headIndex);
+        final Map<Integer, TreeNode> employees = new HashMap<>();
+        employees.put(headIndex, root);
+        for (int i = 0 ; i < managers.length ; i++) {
+            int managerId = managers[i];
+            if (managerId == -1) continue;
+            TreeNode manager = employees.getOrDefault(managerId, new TreeNode(managerId));
+            TreeNode subordinate = employees.getOrDefault(i, new TreeNode(i));
+            manager.addSubordinate(subordinate);
+            if (!employees.containsKey(managerId)) employees.put(managerId, manager);
+            if (!employees.containsKey(i)) employees.put(i, subordinate);
+        }
+        return root;
+    }
+}