Number of Ways to Select Buildings LeetCode solution in Java

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class Solution {
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  public long numberOfWays(String s) {
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    int zero = 0; // Individual zeroes count
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    long zeroOne = 0; // Number of combinations of 01s
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    int one = 0; // Individual ones count
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    long oneZero = 0; // Number of combinations of 10s
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    long tot = 0; // Final answer
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    for (char ch : s.toCharArray()) {
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      if (ch == '0') {
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        zero++;
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        if (one > 0)
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          oneZero +=
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              one; // Each of the previously found 1s can pair up with the current 0 to form 10
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        if (zeroOne > 0)
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          tot +=
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              zeroOne; // Each of the previously formed 01 can form a triplet with the current 0 to
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        // form 010
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      } else {
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        one++;
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        if (zero > 0) zeroOne += zero; // Each of the previously found 0s can pair to form 01
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        if (oneZero > 0) tot += oneZero; // Each of the previously formed 10 can form 101
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      }
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    }
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    return tot;
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  }
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}