First Letter to Appear Twice LeetCode solution in C++

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class Solution {
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 public:
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  char repeatedCharacter(string s) {
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    unordered_map<char, int> mp; // for storing occurrences of char
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    char ans;
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    for (auto it : s) {
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      if (mp.find(it) != mp.end()) // any char which comes twice first will be the ans;
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      {
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        ans = it;
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        break;
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      }
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      mp[it]++; // increase the count of char
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    }
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    return ans;
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  }
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};