Problem
You are given a 0-indexed integer array tasks, where tasks[i] represents the difficulty level of a task. In each round, you can complete either 2 or 3 tasks of the same difficulty level.
Return **the *minimum* rounds required to complete all the tasks, or -1 if it is not possible to complete all the tasks.**
Example 1:
Input: tasks = [2,2,3,3,2,4,4,4,4,4]
Output: 4
Explanation: To complete all the tasks, a possible plan is:
- In the first round, you complete 3 tasks of difficulty level 2.
- In the second round, you complete 2 tasks of difficulty level 3.
- In the third round, you complete 3 tasks of difficulty level 4.
- In the fourth round, you complete 2 tasks of difficulty level 4.
It can be shown that all the tasks cannot be completed in fewer than 4 rounds, so the answer is 4.
Example 2:
Input: tasks = [2,3,3]
Output: -1
Explanation: There is only 1 task of difficulty level 2, but in each round, you can only complete either 2 or 3 tasks of the same difficulty level. Hence, you cannot complete all the tasks, and the answer is -1.
Constraints:
1 <= tasks.length <= 1051 <= tasks[i] <= 109
Solution
/**
* @param {number[]} tasks
* @return {number}
*/
var minimumRounds = function(tasks) {
var map = {};
for (var i = 0; i < tasks.length; i++) {
if (!map[tasks[i]]) map[tasks[i]] = 0;
map[tasks[i]]++;
}
var keys = Object.keys(map);
var res = 0;
for (var j = 0; j < keys.length; j++) {
if (map[keys[j]] === 1) return -1;
res += Math.ceil(map[keys[j]] / 3);
}
return res;
};
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(n).