private static void findTheBestReplacement()

in src/org/intellij/grammar/generator/RuleGraphHelper.java [734:778]
44 lines of code
21 McCabe index (conditional complexity)

  private static void findTheBestReplacement(Map<BnfRule, BnfRule> rulesAndAlts,
                                             List<Map.Entry<BnfRule, Collection<BnfRule>>> supers) {
    BitSet bits = new BitSet(rulesAndAlts.size());
    int minI = -1, minC = -1, minS = -1;
    for (int len = Math.min(16, supers.size()), i = (1 << len) - 1; i > 0; i --) {
      if (minC != -1 && Integer.bitCount(i) > minC) continue;
      int curC = 0, curS = 0;
      bits.set(0, rulesAndAlts.size(), true);
      for (int j = 0, bit = 1; j < len; j ++, bit <<= 1) {
        if ((i & bit) == 0) continue;
        Collection<BnfRule> vals = supers.get(j).getValue();
        curC += 1;
        curS += vals.size();
        if (bits.isEmpty()) continue;

        int k = 0;
        for (Map.Entry<BnfRule, BnfRule> e : rulesAndAlts.entrySet()) {
          if (bits.get(k)) {
            if (vals.contains(e.getKey()) || vals.contains(e.getValue())) {
              bits.set(k, false);
            }
          }
          k ++;
        }
        if (!bits.isEmpty()) {
          curC += bits.cardinality();
          curS += bits.cardinality();
        }
      }
      if (minC == -1 || minC > curC || minC == curC && minS > curS) {
        minC = curC;
        minS = curS;
        minI = i;
      }
    }
    for (Map.Entry<BnfRule, BnfRule> e : rulesAndAlts.entrySet()) {
      for (int len = supers.size(), j = 0, bit = 1; j < len; j++, bit <<= 1) {
        if ((minI & bit) == 0) continue;
        Collection<BnfRule> vals = supers.get(j).getValue();
        if (vals.contains(e.getKey()) || vals.contains(e.getValue())) {
          e.setValue(supers.get(j).getKey());
        }
      }
    }
  }