Join Multidimension Arrays - arrays

Question

I have multiple arrays of different sizes, for instance:
let array1 = [[1, 2, 3], [1, 2, 3]]
let array2 = [[1, 2], [1, 2]]
let array3 = [[1, 2], [1, 2], [1, 2]]
And I wanna join them together so I get the final array:
let finalArray = [[1, 2, 3, 1, 2, 1, 2], [1, 2, 3, 1, 2, 1, 2], [1, 2]]
Any ideia on how can I achieve this goal in a efficient way?

Answer 1

Try like this:
var finalArray:[[Int]] = []
for index in 0..<max(array1.count,array2.count,array3.count) {
finalArray.append([])
if index < array1.count {
finalArray[index].appendContentsOf(array1[index])
}
if index < array2.count {
finalArray[index].appendContentsOf(array2[index])
}
if index < array3.count{
finalArray[index].appendContentsOf(array3[index])
}
}
finalArray // [[1, 2, 3, 1, 2, 1, 2], [1, 2, 3, 1, 2, 1, 2], [1, 2]]

Answer 2

How about:
var arrays = [array1, array2, array3];
var maxSize = Math.max.apply(null, arrays.map(function(a){ return a.length }))
var result = [];
for (var i = 0; i < arrays.length; i++) {
result[i] = [];
for (var j = 0; j < maxSize; j++) {
if (arrays[j][i]) {
result[i] = result[i].concat(arrays[j][i]);
}
}
}
This assumes that what you want to do is end up with a result array that has the same number of elements as the largest input array, putting together the elements in the same position in the input arrays into the output array in the same order as the original arrays.

Answer 3

zip is the obvious function needed to combine the arrays but it is not able to handle the uneven lengths and the map calls may not be as efficient as a C-like algorithm in this case. However as an exercise, here is a more functional approach IF the arrays can be preprocessed to include empty arrays for missing data
let z12 = zip(array1, array2)
let z123 = zip(z12, array3)
let answer = z123.map { [$0.0.0, $0.0.1, $0.1].flatMap { $0 } }
I have changed the arrays from let to var so that they can be appended and I have changed the data for indices 1 to make the answer more obviously correct.