Easy to understand C++ Solution using set  SC:O(n) ✅✅
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\nI used the set to store the numbers in sorted order.\n\n# Complexity\n- T
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\nI used the set to store the numbers in sorted order.\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity: O(n)\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```\nclass Solution {\npublic:\n    int findMaxK(vector<int>& nums) {\n        set <int> s;\n        for(int i:nums) s.insert(i);\n        int mini=INT_MIN;\n        for(auto it:s){\n            if(it<0){\n                if(s.find(abs(it))!=s.end()){\n                    mini=max(abs(it),mini);\n                }\n            }\n        }\n        if(mini!=INT_MIN)\n            return mini;\n            else return -1;\n    }\n};\n```
['Array', 'C++']