Number of Wonderful Substrings LeetCode solution in Java

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class Solution {
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  public long wonderfulSubstrings(String word) {
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    int n = word.length();
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    long count = 0;
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    long[] freq =
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        new long
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            [(1 << 10) + 1]; // Since we have to take only 2^10 possibilies, we can avoid an HashMap
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    freq[0] = 1;
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    int res =
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        0; // initialize the frequency of 0000000000 as 1 because when no element is encountered,
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    // then th bitmask is 0
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    for (int i = 0; i < n; i++) {
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      int mask = (1 << (word.charAt(i) - 'a'));
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      res ^=
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          mask; // toggling bit of the current character to make it from odd to even OR even to odd
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      int chkMask = 1;
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      count += freq[res];
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      for (int j = 1;
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          j <= 10;
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          j++) { // Loop for checking all possiblities of different places of the Different Bit
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        count += freq[chkMask ^ res];
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        chkMask <<= 1;
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      }
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      freq[res]++; // increasing the frequency of the current bitmask
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    }
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    return count;
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  }
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}