class Solution {
public:
    vector<int> asteroidCollision(vector<int>& asteroids) {
        int n = asteroids.size();
        vector<int> res;
        for(int i = 0; i < n; ++i)
        {
            
            if(asteroids[i] < 0) //move to the left, possibly collide to the left asteroid
            {
                while(!res.empty() && res.back() > 0 && res.back() + asteroids[i] < 0)
                    res.pop_back();
                if(res.empty() || res.back() < 0)
                    res.push_back(asteroids[i]);
                else if(res.back() + asteroids[i] == 0)
                    res.pop_back();
            }
            else
                res.push_back(asteroids[i]);
        }
        return res;
    }
};