Balloons are represented as intervals on the x-axis. An arrow at position bursts all balloons where . Find minimum arrows to burst all balloons.
Example: [[10,16], [2,8], [1,6], [7,12]]. One arrow at bursts [2,8] and [1,6]. One arrow at bursts [10,16] and [7,12]. Total: arrows.
How is this related to activity selection? Tricky: minimum arrows = number of non-overlapping groups. Each group of overlapping balloons needs one arrow.