CODEWITHSUNDEEP
javagroovy
Sulteric
Sulteric

Reputation: 527

Finding the 50 cheapest non-matching prices

Given an array of prices (such as 341.95) how would I go about finding the 50 cheapest prices?

The trick is some of the prices in the array could match and the list of 50 should be unique prices. For example if there are 6 prices in there for 123.45 I only want one in my final list of 50. There can't be any duplicates.

I was thinking that the best way would be to take that array and suck it into a second array, filtering out any matching numbers but that's easier said than done.

Upvotes: 0

Views: 85

Answers (6)

bdkosher
bdkosher

Reputation: 5883

If you have an array of Double objects, you can use the Groovy JDK's toUnique, sort, and take methods to find the lowest 50 prices.

// generate some random prices
def r = new Random()
Double[] allPrices = (0..100).collect { (r.nextDouble() * 100).trunc(2) }

Double[] lowestPrices = allPrices.toUnique().sort().take(50)

Hat tip to @cfrick for the suggestion to use take instead of the range and Math.min syntax.

Upvotes: 0

Prakash Thete
Prakash Thete

Reputation: 3892

Here is the groovier solution to your problem 

//priceArray is your input array
def firstFiftyPrices = priceArray.unique().sort()​.take(50)​

Upvotes: 1

Sulteric
Sulteric

Reputation: 527

Based on everyones input I came up with this and it appears to work. lowestPrices is my list of prices, thanks everyone!

 Object[] st = lowestPrices.toArray();
 for (Object s : st) {
      if (lowestPrices.indexOf(s) != lowestPrices.lastIndexOf(s)) {
           lowestPrices.remove(lowestPrices.lastIndexOf(s));
      }
  }

  System.out.println("Distinct List " + lowestPrices)

Upvotes: 0

slim
slim

Reputation: 41213

Using Java 8 streams:

int[] lowestPrices = Arrays.stream(prices)
   .sorted()
   .distinct()
   .limit(50)
   .toArray();

Note that I've used int[] even though you used "123.45" as an example. Using floating point for monetary values is a terrible idea, so represent $123.45 as 12345 cents.

Upvotes: 2

Ishnark
Ishnark

Reputation: 681

Iterate through the array, add each item to a TreeSet, and then return a list of the first 50 elements.

Upvotes: 0

ControlAltDel
ControlAltDel

Reputation: 35011

Optimal in place solution is

  1. Sort the array
  2. Iterate ascending (start with the cheapest) and add each new number (that you didn't see in the last iteration) in succession

Upvotes: 1

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