Best way to take a set of geohashes and determine which ones are neighbors?

[Broham]

I'm not sure if this is the right place for a questions like this, if it's not I apologize. I'm trying to figure out the optimal way to take a list of geohashes and return a sub-list that contains the geohashes that are direct neighbors or have direct neighbors in common (aka - creating groups of contiguous geohashes).

The only way I can think to do this is by looping through the geohashes, getting neighbors and adding them to a new list. Something like the psudo code below:

startingGeoHashes = ["9qczj5t",
                     "9qczj5s", # directly west of the above
                     "9qczj5e", # directly west of the above
                     "9qczjhh" # not a direct neighbor
]
neighborGroup = []
foreach startingGeoHash in startingGeohashes
   if any of startingGeoHashes in getGeoHashNeighbors(startingGeoHash):
      add both to neighborGroups if they aren't already in there

But I'm wondering if there is a set based approach that could return the subset of direct neighbors without looping through ever record and getting the neighbors. Is this possible?