Charles - 1 year ago 52

Ruby Question

My list contains

`User1, 0`

`User2, 50`

`User3, 30`

`User1, 50`

`User3, 68`

How do I get rid of the duplicates, but take the largest value out of them?

Like need to contain this:

`User1, 50`

`User2, 50`

`User3, 68`

`User1, 0`

`User3, 30`

Answer Source

There are many ways to do that. Here's are three.

```
arr = [[:User1, 0], [:User2, 50], [:User3, 30], [:User1, 50], [:User3, 68]]
```

**#1 Use Hash#update (aka Hash#merge!)**

```
arr.each_with_object({}) { |(u,x),h| h.update(u=>x) { |_,o,n| [o,n].max } }.to_a
#=> [[:User1, 50], [:User2, 50], [:User3, 68]]
```

**#2 Order the elements by the second value (using Enumerable#sort_by) and convert to a hash**

```
arr.sort_by(&:last).to_h
#=> {:User1=>50, :User3=>68, :User2=>50}
```

**#3 Use Enumerable#group_by**

```
arr.group_by(&:first).map { |k,v| [k, v.map(&:last).max] }
#=> [[:User1, 50], [:User2, 50], [:User3, 68]]
```