2024-03-19 Daily Challenge

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Today I have done leetcode's March LeetCoding Challenge with cpp.

March LeetCoding Challenge 19

Description

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

Solution

class Solution {
public:
  int leastInterval(vector<char>& tasks, int n) {
    unordered_map<char, int> mp;
    int all = tasks.size();
    int maximum = 0;
    for(auto c : tasks) {
      mp[c] += 1;
      if(mp[c] > maximum) {
        maximum = mp[c];
      }
    }
    int answer = (maximum-1) * (n+1);
    for(auto [_, cnt] : mp) {
      if(cnt == maximum) answer += 1;
    }
    return max(answer, all);
  }
};
Algorithm