code: private void fixNCNTypes(String[] symbs, int[][] graph) {
          for (int v = 0; v < graph.length; v++) {
              if ("NCN+".equals(symbs[v])) {
                  boolean foundCNN = false;
                  for (int w : graph[v]) {
                      foundCNN = foundCNN || "CNN+".equals(symbs[w]) || "CIM+".equals(symbs[w]);
                  }
                  if (!foundCNN) {
                      symbs[v] = "NC=N";
                  }
              }
          }
      }
docs: Special case, 'NCN+' matches entries that the validation suite say should actually be 'NC=N'.
  We can achieve 100% compliance by checking if NCN+ is still next to CNN+ or CIM+ after
  aromatic types are assigned
  
  @param symbs symbolic types
  @param graph adjacency list graph