https://leetcode.com/problems/minimum-number-of-arrows-to-burst-balloons/

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 xstart and xend bursts by an arrow shot at x if 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 where points[i] = [xstart, xend], return the minimum number of arrows that must be shot to burst all balloons.

Example 1:

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).

Example 2:

Input: points = [[1,2],[3,4],[5,6],[7,8]]

Output: 4

Example 3:

Input: points = [[1,2],[2,3],[3,4],[4,5]]

Output: 2

Example 4:

Input: points = [[1,2]]

Output: 1

Example 5:

Input: points = [[2,3],[2,3]]

Output: 1

Constraints:

0 <= points.length <= 10^4

points[i].length == 2

-2^31 <= xstart < xend <= 2^31 - 1

1 | class Solution { |