能重疊的區域能一起射爆
所以先排序
再取重合的區域
看一共有幾個這樣的區域

class Solution:
    def findMinArrowShots(self, points):
        """
        :type points: List[List[int]]
        :rtype: int
        """
        if not points: return 0
        sp=sorted(points,key=lambda points:points[0])
        count=0
        pre=sp[0]
        for i in range(len(sp)):
            if sp[i][0]<=pre[1]:
                pre=[sp[i][0],min(pre[1],sp[i][1])]
            else:
                pre=sp[i]
                count+=1 
        return count+1