Solution.go

func getNumberOfBacklogOrders(orders [][]int) (ans int) {
	sell := hp{}
	buy := hp{}
	for _, e := range orders {
		p, a, t := e[0], e[1], e[2]
		if t == 0 {
			for a > 0 && len(sell) > 0 && sell[0].p <= p {
				q := heap.Pop(&sell).(pair)
				x, y := q.p, q.a
				if a >= y {
					a -= y
				} else {
					heap.Push(&sell, pair{x, y - a})
					a = 0
				}
			}
			if a > 0 {
				heap.Push(&buy, pair{-p, a})
			}
		} else {
			for a > 0 && len(buy) > 0 && -buy[0].p >= p {
				q := heap.Pop(&buy).(pair)
				x, y := q.p, q.a
				if a >= y {
					a -= y
				} else {
					heap.Push(&buy, pair{x, y - a})
					a = 0
				}
			}
			if a > 0 {
				heap.Push(&sell, pair{p, a})
			}
		}
	}
	const mod int = 1e9 + 7
	for len(buy) > 0 {
		ans += heap.Pop(&buy).(pair).a
	}
	for len(sell) > 0 {
		ans += heap.Pop(&sell).(pair).a
	}
	return ans % mod
}

type pair struct{ p, a int }
type hp []pair

func (h hp) Len() int            { return len(h) }
func (h hp) Less(i, j int) bool  { return h[i].p < h[j].p }
func (h hp) Swap(i, j int)       { h[i], h[j] = h[j], h[i] }
func (h *hp) Push(v interface{}) { *h = append(*h, v.(pair)) }
func (h *hp) Pop() interface{}   { a := *h; v := a[len(a)-1]; *h = a[:len(a)-1]; return v }