go: create 0621-task-scheduler.go

go/0621-task-scheduler.go

@@ -0,0 +1,61 @@
+type MaxHeap []int
+
+func (h MaxHeap) Len() int            { return len(h) }
+func (h MaxHeap) Less(i, j int) bool  { return h[i] < h[j] }
+func (h MaxHeap) Swap(i, j int)       { h[i], h[j] = h[j], h[i] }
+func (h *MaxHeap) Push(x interface{}) { *h = append(*h, x.(int)) }
+func (h *MaxHeap) Pop() interface{} {
+	old := *h
+	n := len(old)
+	x := old[n-1]
+	*h = old[0 : n-1]
+	return x
+}
+
+func leastInterval(tasks []byte, n int) int {
+	// each task 1 unit time
+	// minimize idle time
+
+	// count the occurance of charater in tasks (list)
+	count := make(map[byte]int, 0)
+	occuranceOfCharaters(count, tasks)
+
+	maxHeap := &MaxHeap{}
+	// adding count values to maxheap
+	for _, value := range count {
+		*maxHeap = append(*maxHeap, -value)
+	}
+	// Heapify the maxHeap
+	heap.Init(maxHeap)
+
+	var time int = 0
+	var deque [][]int
+
+	for maxHeap.Len() != 0 || len(deque) != 0 {
+		time += 1
+		if maxHeap.Len() != 0 {
+			cnt := 1 + heap.Pop(maxHeap).(int)
+			if cnt != 0 {
+				deque = append(deque, []int{cnt, time + n})
+			}
+		}
+
+		if len(deque) != 0 && deque[0][1] == time {
+			// first push the left most element to deque
+			heap.Push(maxHeap, deque[0][0])
+			// deque pop left (pop first)
+			deque = deque[1:]
+		}
+	}
+	return time
+}
+
+func occuranceOfCharaters(count map[byte]int, tasks []byte) {
+	for _, val := range tasks {
+		if cnt, ok := count[val]; ok {
+			count[val] = cnt + 1
+			continue
+		}
+		count[val] = 1
+	}
+}