Java : Find the Best N In Your List Based on a Figure of Merit (FOM)

Here's the deal : you have two ArrayLists, one keeps the name of something and the other, the FOM associated with that entity. For example, a list of usernames and the FOM is number of followers on Instagram.

Someone asks you : tell me the 10 most popular people. If you get the indexes of these ten (in an array0, then you do a simple for loop to 10 and dump out the name_ArrayList.get(i) to spit out the answer.

How do you get the indexes of the top N? Here's how :

public int[] bestN(int N){

  int [] maxes = new int[N];

  int [] inds = new int[N];

  // N passes.

  for( int ptr = 0; ptr < N; ptr++){

    maxes[ptr] = 0;

    inds[ptr] = 0;

    for( int i = 0; i < FOM_list.size(); i++ ){

      if( FOM_list.get(i) > maxes[ptr] ){

        if( (0 ==ptr) || (ptr > 0 && FOM_list.get(i) < maxes[ptr-1]) ){

// if it's the first item, nothing else to consider. Go ahead and enter. Else, ensure that this

// entry is not higher (in FOM) than the one that's supposed to be better than it 😊

          maxes[ptr] = FOM_list.get(i);

          inds[ptr] = i;

        }

      }

    }

  }

  return inds;

}

And then :

createTheArrayLists();

int [] best10 = new int[10];

best10 = bestN(10);

System.out.println("Most popular bloggers:");

for( int i = 0; i< 10; i++){

  System.out.println(bloggerAList.get(best10[i]) + ": " + followers.get(best10[i]));

}