CODEWITHSUNDEEP
algorithmgroovyranking
Richard Paul
Richard Paul

Reputation: 286

Simple ranking algorithm in Groovy

I have a short groovy algorithm for assigning rankings to food based on their rating. This can be run in the groovy console. The code works perfectly, but I'm wondering if there is a more Groovy or functional way of writing the code. Thinking it would be nice to get rid of the previousItem and rank local variables if possible.

def food = [
  [name:'Chocolate Brownie',rating:5.5, rank:null],
  [name:'Fudge', rating:2.1, rank:null],
  [name:'Pizza',rating:3.4, rank:null],
  [name:'Icecream', rating:2.1, rank:null],
  [name:'Cabbage', rating:1.4, rank:null]]

food.sort { -it.rating }

def previousItem = food[0]
def rank = 1
previousItem.rank = rank
food.each { item ->
  if (item.rating == previousItem.rating) {
    item.rank = previousItem.rank
  } else {
    item.rank = rank
  }
  previousItem = item
  rank++
}

assert food[0].rank == 1
assert food[1].rank == 2
assert food[2].rank == 3
assert food[3].rank == 3    // Note same rating = same rank
assert food[4].rank == 5    // Note, 4 skipped as we have two at rank 3

Suggestions?

Upvotes: 1

Views: 1303

Answers (3)

Ted Naleid
Ted Naleid

Reputation: 26801

Here's another alternative that doesn't use "local defs" with the groovy inject method:

food.sort { -it.rating }.inject([index: 0]) { map, current ->
    current.rank = (current.rating == map.lastRating ? map.lastRank : map.index + 1)
    [ lastRating: current.rating, lastRank: current.rank, index: map.index + 1 ]
}

Upvotes: 0

Christoph Metzendorf
Christoph Metzendorf

Reputation: 8078

This is my solution:

def rank = 1
def groupedByRating = food.groupBy { -it.rating }
groupedByRating.sort().each { rating, items ->
  items.each { it.rank = rank }
  rank += items.size()
}

Upvotes: 2

Daniel Engmann
Daniel Engmann

Reputation: 2850

I didn't try it, but maybe this could work.

food.eachWithIndex { item, i ->
    if( i>0 && food[i-1].rating == item.rating ) 
        item.rank = food[i-1].rank
    else
        item.rank = i + 1
}

Upvotes: 0

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