Number of Substrings Containing All Three Characters LeetCode solution in Java

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class Solution {
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  public int numberOfSubstrings(String s) {
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    int a = 0, b = 0, c = 0, count = 0;
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    for (int i = 0; i < s.length(); i++) {
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      switch (s.charAt(i)) {
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        case 'a':
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          ++a;
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          break;
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        case 'b':
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          ++b;
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          break;
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        case 'c':
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          ++c;
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          break;
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      }
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      if (a > 0 && b > 0 && c > 0) {
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        while (a > 0 && b > 0 && c > 0) {
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          char farLeft = s.charAt(i - a - b - c + 1);
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          switch (farLeft) {
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            case 'a':
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              {
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                --a;
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                count += doCount(s, i);
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                break;
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              }
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            case 'b':
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              {
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                --b;
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                count += doCount(s, i);
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                break;
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              }
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            case 'c':
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              {
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                --c;
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                count += doCount(s, i);
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                break;
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              }
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          }
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        }
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      }
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    }
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    return count;
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  }
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  private int doCount(String s, int i) {
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    int count = 0;
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    int n = s.length() - i;
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    if (n > 0) {
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      count += n;
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    }
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    return count;
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  }
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}