Fastest/One-liner way to collect duplicates in Ruby Array?

Question

What's the fastest/one-liner way to convert an array like this: `[1, 1, 1, 1, 2, 2, 3, 5, 5, 5, 8, 13, 21, 21, 21]` ...into an array of objects like this: `[{1 => 4}, {2 => 2}, {3 => 1}, {5 => 3}, {8 => 1}, {13 => 1}, {21 => 3}]`

Accepted Answer

To achieve your desired format, you could append a call to map to your solution:

```
array.inject({}) { |h,v| h[v] ||= 0; h[v] += 1; h }.map {|k, v| {k => v}}
```

Although it still is a one-liner, it starts to get messy.

Fastest/One-liner way to collect duplicates in Ruby Array?

Solution

Problem