621 Task Scheduler

Task Scheduler

You are given an array of CPU tasks, each represented by letters A to Z, and a cooling time, n. Each cycle or interval allows the completion of one task. Tasks can be completed in any order, but there’s a constraint: identical tasks must be separated by at least n intervals due to cooling time.

​Return the minimum number of intervals required to complete all tasks.

 

Example 1:

**Input:** tasks = ["A","A","A","B","B","B"], n = 2 **Output:** 8 **Explanation:** A possible sequence is: A -> B -> idle -> A -> B -> idle -> A -> B. After completing task A, you must wait two cycles before doing A again. The same applies to task B. In the 3rd interval, neither A nor B can be done, so you idle. By the 4th cycle, you can do A again as 2 intervals have passed. Example 2:

**Input:** tasks = ["A","C","A","B","D","B"], n = 1 **Output:** 6 **Explanation:** A possible sequence is: A -> B -> C -> D -> A -> B. With a cooling interval of 1, you can repeat a task after just one other task. Example 3:

**Input:** tasks = ["A","A","A", "B","B","B"], n = 3 **Output:** 10 **Explanation:** A possible sequence is: A -> B -> idle -> idle -> A -> B -> idle -> idle -> A -> B. There are only two types of tasks, A and B, which need to be separated by 3 intervals. This leads to idling twice between repetitions of these tasks.   **Constraints:** 1 <= tasks.length <= 104 tasks[i] is an uppercase English letter. 0 <= n <= 100 ```csharp public class Solution { public int LeastInterval(char[] tasks, int n) { SortedList<char , int> dict = new SortedList<char , int>(); for(int i = 0 ; i < tasks.Length ; i ++) { if(dict.ContainsKey(tasks[i])) { dict[tasks[i]] = dict[tasks[i]] + 1; } else { dict.Add(tasks[i] , 1); } } var t = dict.OrderByDescending(x => x.Value); int availableSpace = (t.First().Value-1)*n; Console.WriteLine(availableSpace); Console.WriteLine(t.First().Value); for(int i = 1 ; i < t.Count() ; i++) { Console.WriteLine(t.ElementAt(i).Value); //in case frequency is same as maximum availableSpace = availableSpace - Math.Min( t.First().Value-1 ,t.ElementAt(i).Value); //Console.WriteLine(availableSpace); } //what to do if availableSpace is negative availableSpace = Math.Max(availableSpace , 0); return availableSpace + tasks.Length; } } ```