[LC735]行星碰撞

    public int[] asteroidCollision(int[] asteroids) {
        Deque<Integer> stack = new ArrayDeque();
        //check every aster from left to right
        for(int aster : asteroids){
            boolean addNewAster = true;
            //keep check until this aster is dead or there is no collision to happen
            while(addNewAster && !stack.isEmpty() && stack.peekLast() > 0 && aster < 0){
                int lastAster = stack.peekLast(), copyAster = -aster;
                if(lastAster <= copyAster) stack.pollLast();
                if(lastAster >= copyAster) addNewAster = false;
            }
            if(addNewAster) stack.addLast(aster);
        }
        int[] rtn = new int[stack.size()];
        for(int i = 0; i < rtn.length ; i++){
            rtn[i] = stack.pollFirst();
        }
        return rtn;
    }