Find Longest Awesome Substring LeetCode solution in C++

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class Solution {
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 public:
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  int longestAwesome(string s) {
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    unordered_map<int, int> map;
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    int mask = 0, maxL = 0;
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    map[mask] = -1;
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    for (int i = 0; i < s.size(); ++i) {
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      int ch = s[i] - '0';
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      mask ^= (1 << ch);
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      if (map.find(mask) != map.end()) {
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        maxL = max(maxL, i - map[mask]);
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      }
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      for (int x = 0; x <= 9; ++x) {
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        int newMask = mask ^ (1 << x);
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        if (map.find(newMask) != map.end()) {
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          maxL = max(maxL, i - map[newMask]);
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        }
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      }
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      if (map.find(mask) == map.end()) {
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        map[mask] = i;
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      }
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    }
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    return maxL;
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  }
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};