added daily challenge

Author: Pasindu-Vishmika

621. Task Scheduler.py

@@ -0,0 +1,13 @@
+class Solution:
+    def leastInterval(self, tasks: List[str], n: int) -> int:
+        freq = [0] * 26
+        for task in tasks:
+            freq[ord(task) - ord('A')] += 1
+        freq.sort()
+        chunk = freq[25] - 1
+        idle = chunk * n
+
+        for i in range(24, -1, -1):
+            idle -= min(chunk, freq[i])
+
+        return len(tasks) + idle if idle >= 0 else len(tasks)