Question

Say I have two arrays, items and removeItems and I wanted any values found in removeItems to be removed from items.

The brute force mechanism would probably be:

var animals = ["cow","dog","frog","cat","whale","salmon","zebra","tuna"];
var nonMammals = ["salmon","frog","tuna","spider"];
var mammals = [];
var isMammal;

for(var i=0;i<animals.length;i++){
   isMammal = true;
   for(var j=0;j<nonMammals;j++){
     if(nonMammals[j] === animals[i]){
       isMammal = false;
       break;
     }
   }
   if(isMammal){
     mammals.push(animals[i]);
   }
}

This is what? O(N^2)? Is there a more efficient way?

Answer 1

That’s actually O(M * N).

Probably you could do better sorting the animals array first, then doing a binary search. You’ll be able to reduce to O(N * log N) – well, that’s if log N < M anyway.

Anyway, if you’re working with JS and that runs client-side, then just try to keep amount of data at minimum, or their browsers will yell at you with every request.