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Problem: 0621-task-scheduler.cpp
Language: C++
Submission URL: https://leetcode.com/problems/task-scheduler/submissions/889595683/

Author: caba5

cpp/0621-task-scheduler.cpp

@@ -8,7 +8,7 @@
     Time: O(n)
     Space: O(1)
 */
-
+/*
 class Solution {
 public:
     int leastInterval(vector<char>& tasks, int n) {
@@ -38,3 +38,36 @@ class Solution {
         return tasks.size() + idles;
     }
 };
+*/
+
+// Time O(n * cooldown)
+class Solution {
+public:
+    int leastInterval(vector<char>& tasks, int n) {
+        priority_queue<int> pq;
+        queue<vector<int>> q;
+        vector<int> counter(26);
+
+        for (int i = 0; i < tasks.size(); ++i)
+            ++counter[tasks[i] - 'A'];
+        for (int i = 0; i < 26; ++i){
+            if (counter[i])
+                pq.push(counter[i]);
+        }
+
+        int time = 0;
+        while (!q.empty() || !pq.empty()){
+            ++time;
+            if (!pq.empty()){
+                if (pq.top() - 1)
+                    q.push({pq.top() - 1, time + n});
+                pq.pop();
+            }
+            if (!q.empty() && q.front()[1] == time){
+                pq.push(q.front()[0]);
+                q.pop();
+            }
+        }
+        return time;
+    }
+};