Group array by nested array - ruby

Question

I have an array in this format:
[
{ day: 1
intervals: [
{
from: 900,
to: 1200
}
]
},
{ day: 2
intervals: [
{
from: 900,
to: 1200
}
]
},
{ day: 3
intervals: [
{
from: 900,
to: 1200
}
]
},
{ day: 4
intervals: [
{
from: 900,
to: 1200
}
]
},
{ day: 5
intervals: [
{
from: 900,
to: 1200
}
]
},
{ day: 6
intervals: [
{
from: 900,
to: 1200
},
{
from: 1300,
to: 2200
}
]
},
{ day: 7
intervals: [
{
from: 900,
to: 1200
},
{
from: 1300,
to: 2200
}
]
}
]
I wan't to group them like this:
[
{ day: 1-5
intervals: [
{
from: 900,
to: 1200
}
]
},
{ day: 6-7
intervals: [
{
from: 900,
to: 1200
},
{
from: 1300,
to: 2200
}
]
}
]
Criteria:
Only group if intervals are the same.
Only group if matches are in chronological order, i.e 1-5 or 1-3, not 1-2-5.
How can this be achieved?

Answer 1

Here's a variation of #joelparkerhenderson's solution that tries to be a bit closer to your requirements re formatting of the output etc.
output = []
grouped = input.group_by do |x|
x[:intervals]
end
grouped.each_pair do |k, v|
days = v.map {|day| day[:day]}
if days.each_cons(2).all? { |d1, d2| d1.next == d2 }
output << {
:days => days.values_at(0,-1).join('-'),
:intervals => k
}
end
end
puts output

Answer 2

This produces the required output:
by_interval = data.inject({}) do | a, e |
i = e[:intervals]
a[i] ||= []
a[i] << e[:day].to_i
a
end
result = by_interval.map do | interval, days |
slices = days.sort.inject([]) do | a, e |
a << [] if a == [] || a.last.last != e - 1
a.last << e
a
end
slices.map do | slice |
{:day => "#{slice.first}-#{slice.last}", :intervals => interval }
end
end
result.flatten!
I'm sure there are better approaches :-)

Answer 3

You need to look into Map Method for an array. You need to remap the array and iterate over it to extract the data you want using your "grouping" logic above.

Answer 4

Extending #Michael Kohl's answer
output = []
grouped = schedules.as_json.group_by do |x|
x['intervals']
end
grouped.each_pair do |k, v|
days = v.map {|day| day['day']}
grouped_days = days.inject([[]]) do |grouped, num|
if grouped.last.count == 0 or grouped.last.last == num - 1
grouped.last << num
else
grouped << [ num ]
end
grouped
end
grouped_days.each do |d|
output << {
heading: d.values_at(0, -1).uniq.join('-'),
interval: k
}
end
end
output
You should probably split that up into separate methods, but you get the idea.