Asteroid Collision LeetCode solution in C++

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class Solution {
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 public:
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  vector<int> asteroidCollision(vector<int> &asteroids) {
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    vector<int> v;
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    stack<int> s;
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    for (auto x : asteroids) {
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      if (x > 0)
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        s.push(x);
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      else {
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        // Case 1: whem top is less than x
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        while (s.size() > 0 && s.top() > 0 && s.top() < -x) {
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          s.pop();
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        }
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        // case 2 : when both of same size
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        if (s.size() > 0 && s.top() == -x) {
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          s.pop();
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        }
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        // case 3: when top is greater
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        else if (s.size() > 0 && s.top() > -x) {
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          // do nothing
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        }
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        // case 4: when same direction
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        else {
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          s.push(x);
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        }
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      }
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    }
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    while (!s.empty()) {
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      v.push_back(s.top());
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      s.pop();
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    }
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    reverse(v.begin(), v.end());
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    return v;
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  }
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};