Update 621

Author: trung-hn

Readme.md

@@ -259,7 +259,7 @@
 | 593  | [Valid Square](src/593.valid-square.py)                                                                                                                              | Medium | O(1)                  | O(1)           | Math                                                                                                 |                                         |           |
 | 605  | [Can Place Flowers](src/605.can-place-flowers.py)                                                                                                                    | Easy   | O(N)                  | O(1)           | Array, Greedy                                                                                        |                                         |           |
 | 611  | [Valid Triangle Number](src/611.valid-triangle-number.py)                                                                                                            | Medium | O(N^2)                | O(1)           | Array, Two Pointers, Binary Search, Greedy, Sorting                                                  |                                         |           |
-| 621  | [Task Scheduler](src/621.task-scheduler.py)                                                                                                                          | Medium | O(N)                  | O(1)           | Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Counting                                  |                                         |           |
+| 621  | [Task Scheduler](src/621.task-scheduler.py)                                                                                                                          | Medium | O(N)                  | O(1)           | Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Counting                                  | Greedy                                         |           |
 | 622  | [Design Circular Queue](src/622.design-circular-queue.py)                                                                                                            | Medium | O(1)                  | O(1)           | Design, Queue                                                                                        |                                         |           |
 | 623  | [Add One Row to Tree](src/623.add-one-row-to-tree.py)                                                                                                                | Medium | O(N)                  | O(N)           | Tree                                                                                                 |                                         |           |
 | 624  | [Maximum Distance in Arrays](src/624.py)                                                                                                                             | Easy   | O(N)                  | O(1)           | Hash Table, Array, Premium                                                                           |                                         | 🔒         |

src/621.task-scheduler.py

@@ -6,6 +6,9 @@
 
 # @lc code=start
 # TAGS: Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Counting
+# REVIEWME: Greedy
+
+import collections
 
 
 class Solution: