优化大块API调用的邮政编码列表

Question

I'm trying hard to find a good solution to an optimization problem that's pretty difficult for me to solve in the best way using JavaScript.

I've got an array to start with, in which each element is another array containing two postal codes. I need to calculate the distance between those postal codes using the Google Maps distance matrix API. The API limits me to 25 "origins" and 25 "destinations" per call, which means I can calculate 625 distances per call. As I've got a huge list of postal codes and only 2500 API calls per day without having to pay for the API usage, I need to optimize those calls the best way possible (+I'm saving the distances locally as a cache).

In code, an example of an array looks like this:

[[10115, 99734],
[99734, 80331],
[80331, 10115],
[81929, 99734]]

There are no duplicates, so no need to worry about that. At the end, by calling

maps.distanceMatrix({
   origins: orArray,
   destinations: destArray
}).asPromise()

I can get the results, but onArray and destArray may only contain 25 postal codes each. I can't find a good solution with good runtime-complexity that would work with over 10000 pairs of postal codes.

To sum up, I need to "convert" the first array into multiple origin and destination arrays, eg into an array where each element again consists of an origin and destination array on which I just loop over and call the API with. I hope I explained the problem cleary enough. It would be awesome if you could give me some ideas on how to solve this the most efficient way as I have been stuck on this for a pretty long time now...

Thank you very much!

Answer 1

I think you could store these pairs in an object ( hash table ) to optimize:

var pairs=[[1,2],[1,3],[4,1]];

var hash={};

pairs.forEach(function(pair){
  if(hash[pair[0]]){
    return hash[pair[0]].push(pair[1]);
  }
  if(hash[pair[1]]){
   return hash[pair[1]].push(pair[0]);
  }
hash[pair[0]]=[pair[1]];
});

Hash should now be:

{
1:[2,3,4]
}

So you can:

for(key in hash)
 apiCall({origins:[key],destinations:hash[key]});

Todo:

{
1:[2,3,4],
5:[2,3,4]
}

could be optimized to:

{origins:[1,5],destinations:[2,3,4]}