How do I do stable sort?
ruby, sorting, stable-sort
Solution
Put the key that you originally wanted to sort by and the index into an array, and sort by that.
a.sort_by.with_index { |(x, y), i| [y, i] }
# => [[:a, 0], [:c, 0], [:d, 0], [:b, 1]]
Problem
How do I stably sort an array? The value I want to sort by can have a lot of duplicates, and I'm not sure which sort algorithm ruby uses. I'm thinking insertion sort would have worked best for me. Example: ``` a = [[:a, 0], [:b, 1], [:c, 0], [:d, 0]] a.sort_by { |x, y| y } # => [[:a, 0], [:d, 0], [:c, 0], [:b, 1]] ``` Looking for ``` [[:a, 0], [:c, 0], [:d, 0], [:b, 1]] ```