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There are some spherical balloons spread in two-dimensional space. For each balloon, provided input is the start and end coordinates of the horizontal diameter. Since it's horizontal, y-coordinates don't matter, and hence the x-coordinates of start and end of the diameter suffice. The start is always smaller than the end.
An arrow can be shot up exactly vertically from different points along the x-axis. A balloon with
xend bursts by an arrow shot at
xstart ≤ x ≤ xend. There is no limit to the number of arrows that can be shot. An arrow once shot keeps traveling up infinitely.
Given an array
points[i] = [xstart, xend], return the minimum number of arrows that must be shot to burst all balloons.
Input: points = [[10,16],[2,8],[1,6],[7,12]] Output: 2 Explanation: One way is to shoot one arrow for example at x = 6 (bursting the balloons [2,8] and [1,6]) and another arrow at x = 11 (bursting the other two balloons).
Input: points = [[1,2],[3,4],[5,6],[7,8]] Output: 4
Input: points = [[1,2],[2,3],[3,4],[4,5]] Output: 2
Input: points = [[1,2]] Output: 1
Input: points = [[2,3],[2,3]] Output: 1
0 <= points.length <= 104
points[i].length == 2
-231 <= xstart < xend <= 231 - 1