#841 · #452 · Minimum Number of Arrows to Burst Balloons(用最少数量的箭引爆气球)

There are spherical balloons taped to a wall at points[i] = [xstart, xend]. An arrow shot vertically at x bursts every balloon whose span contains x. Return the minimum number of arrows to burst all balloons. Constraints: 1 <= points.length <= 10^5, -2^31 <= xstart <= xend <= 2^31 - 1.