反转扑克牌问题，扑克牌排列在桌面上，每次反转一定区间的扑克牌，或者询问某一个区间内的扑克牌总共被反转了几次，使用线段树，可以处理大规模数据（扑克牌数量很多）(Reversal of playing cards: playing cards are arranged on the table. Each time you reverse a certain range of cards, or ask the playing cards in a certain range are reversed several times. Using the line segment tree, you can process large-scale data (there are a lot of cards))