C++ clean code using unordered map
\nclass Solution {\npublic:\n    string greatestLetter(string s) {\n        unordered_map<char,int>ump;\n        for(int i=0;i<s.size();i++)\n        {\n       
```\nclass Solution {\npublic:\n    string greatestLetter(string s) {\n        unordered_map<char,int>ump;\n        for(int i=0;i<s.size();i++)\n        {\n            if(s[i]>=\'a\'&&s[i]<=\'z\')\n                ump[s[i]-32]=1;\n        }\n        for(int i=0;i<s.size();i++)\n        {\n            if(ump[s[i]]==1)\n                ump[s[i]]=2;\n        }\n        string ans="";\n        for(auto x:ump)\n        {\n            if(x.second==2)\n            {\n                if(ans.size()==0)\n                    ans+=x.first;\n                else\n                {\n                    if(x.first>ans[0])\n                        ans[0]=x.first;\n                }\n            }\n        }return ans;\n    }\n};\n```
['C']