Solution.go

func scheduleCourse(courses [][]int) int {
	sort.Slice(courses, func(i, j int) bool { return courses[i][1] < courses[j][1] })
	pq := &hp{}
	s := 0
	for _, e := range courses {
		duration, last := e[0], e[1]
		s += duration
		pq.push(duration)
		for s > last {
			s -= pq.pop()
		}
	}
	return pq.Len()
}

type hp struct{ sort.IntSlice }

func (h hp) Less(i, j int) bool { return h.IntSlice[i] > h.IntSlice[j] }
func (h *hp) Push(v any)        { h.IntSlice = append(h.IntSlice, v.(int)) }
func (h *hp) Pop() any {
	a := h.IntSlice
	v := a[len(a)-1]
	h.IntSlice = a[:len(a)-1]
	return v
}
func (h *hp) push(v int) { heap.Push(h, v) }
func (h *hp) pop() int   { return heap.Pop(h).(int) }