Medium
Given nums of asteroids (absolute value = size, sign = direction: positive right, negative left), return the state after all collisions. Two moving toward each other: the smaller explodes; equal sizes both explode. Same direction never collide.
Input: asteroids = [5,10,-5] Output: [5,10]
Input: asteroids = [8,-8] Output: []
Input: asteroids = [10,2,-5] Output: [10]