Given two dictionaries containing arrays of different capacities add elements to the lesser populated array - swift

Question

So given this data
var data =
["groupA":
[1, 2, 3, 4, 5, 6],
"groupB":
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]]
I want this output:
["groupA":
[0, 0, 0, 0, 1, 2, 3, 4, 5, 6],
"groupB":
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]]
This is the best answer I was able to come up with but I feel like its lacking as I have access to the accumulator that I want to mutate within the reduce function.
let maxElement = data.reduce(data.first!) { (acc, obj) in
return acc.value.count > obj.value.count ? acc : obj
}
for dict in data {
if dict.value.count < maxElement.value.count {
var mutableValues = dict.value
mutableValues.insert(0, at: 0)
data[dict.key] = mutableValues
}
}
I think I'm not understanding how to best refactor my reduce function.

Answer 1

If, like me, you don't like for loops, how about this:
data.reduce(data.values.reduce(0){max($0,$1.count)})
{ data[$1.0] = Array(repeating:0,count:$0-$1.1.count) + $1.1; return $0}

Answer 2

You can get the maximum count of your arrays and create an array of zeros with the difference to append to the lesser populated arrays as follow:
var dict: [String:[Int]] = ["groupA": [1, 2, 3, 4, 5, 6],
"groupB": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]]
let maxCount = dict.values.map{ $0.count }.max() ?? 0
for (key, value) in dict {
let difference = maxCount - value.count
if difference > 0 {
dict[key] = repeatElement(0, count: difference) + value
}
}
print(dict) // ["groupB": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], "groupA": [0, 0, 0, 0, 1, 2, 3, 4, 5, 6]]

Answer 3

As per your question you need to refactor your code for the reduce function, I did it the following way.
Hope this helps,
let maxElement = data.reduce(data.first!) {
$0.value.count > $1.value.count ? $0 : $1
}
further I modified the code you provided to achieve the results you were trying.
and the code worked well for me.
let maxElement = data.reduce(data.first!) {
$0.value.count > $1.value.count ? $0 : $1
}
let minElement = data.reduce(data.first!) {
$0.value.count < $1.value.count ? $0 : $1
}
for dict in data {
if dict.value.count < maxElement.value.count {
var mutableValues = minElement.value
let arrayOfZeros = Array(repeating: 0, count: maxElement.value.count - minElement.value.count)
mutableValues.insert(contentsOf: arrayOfZeros, at: 0)
data[dict.key] = mutableValues
}
}