task scheduler

 1from collections import Counter
 2
 3class Solution:
 4    def leastInterval(self, tasks, n):
 5        freq = sorted(Counter([ord(x) - ord('A') for x in tasks]).values())
 6        f_max = freq.pop()
 7        idle_time = (f_max - 1) * n
 8        while freq and idle_time > 0:
 9            idle_time -= min(f_max - 1, freq.pop())
10        idle_time = idle_time if idle_time >= 0 else 0
11        return idle_time + len(tasks)
12
13tasks = ['A', 'A', 'A', 'B', 'B', 'C']
14r = Solution().leastInterval(tasks, 2)
15print(r)