Number of Wonderful Substrings LeetCode solution in C++

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class Solution {
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 public:
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  long long wonderfulSubstrings(string word) {
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    int n = word.length();
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    int mask = 0;
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    unordered_map<int, int> m;
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    m[0]++;
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    long long int ans = 0;
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    for (int i = 0; i < n; i++) {
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      mask = mask ^ (1 << (word[i] - 'a'));
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      int temp = mask;
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      int j = 0;
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      while (j <= 9) {
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        int x = temp ^ (1 << j);
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        ans += m[x];
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        j++;
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      }
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      ans += m[mask];
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      m[mask]++;
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    }
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    return ans;
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  }
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};