I've this familiar question that looks like permutation/combination of the Math world.
How can I achieve the following via ruby?
badges = "1-2-3"
badge_cascade = []
badges.split("-").each do |b|
badge_cascade << b
end
Gives: => ["1", "2", "3"]
But I want it to be is:
=> ["1", "2", "3",
"1-2", "2-3", "3-1", "2-1", "3-2", "1-3",
"1-2-3", "2-3-1", "3-1-2"]
Functional approach:
bs = "1-2-3".split("-")
strings = 1.upto(bs.size).flat_map do |n|
bs.permutation(n).map { |vs| vs.join("-") }
end
#=> ["1", "2", "3", "1-2", "1-3", "2-1", "2-3", "3-1", "3-2", "1-2-3", "1-3-2", "2-1-3", "2-3-1", "3-1-2", "3-2-1"]
You ned to use Array#permutation method in order to get all permutations:
arr = "1-2-3".split '-' # => ["1", "2", "3"]
res = (1..arr.length).reduce([]) { |res, length|
res += arr.permutation(length).to_a
}.map {|arr| arr.join('-')}
puts res.inspect
# => ["1", "2", "3", "1-2", "1-3", "2-1", "2-3", "3-1", "3-2", "1-2-3", "1-3-2", "2-1-3", "2-3-1", "3-1-2", "3-2-1"]
Let me explain the code:
You split string into array passing separator '-' to String#split method
You need all permutations of length 1, 2, 3. Range 1..arr.length represents all these lengths.
You collect an array of all permutations using Enumerable#reduce.
You will get array of arrays here:
[["1"], ["2"], ["3"], ["1", "2"], ["1", "3"], ["2", "1"], ["2", "3"], ["3", "1"], ["3", "2"], ["1", "2", "3"], ["1", "3", "2"], ["2", "1", "3"], ["2", "3", "1"], ["3", "1", "2"], ["3", "2", "1"]]
You transform all subarrays of this array into strings using Array#join with your '-' separator inside of Enumerable#map
Array#permutation(n) will give you all the permutations of length n as an Array of Arrays so you can call this with each length between 1 and the number of digits in badges. The final step is to map these all back into strings delimited with -.
badges = "1-2-3"
badges_split = badges.split('-')
permutations = []
(1..badges_split.size).each do |n|
permutations += badges_split.permutation(n).to_a
end
result = permutations.map { |permutation| permutation.join('-') }
Update: I think Alex's use of reduce is a more elegant approach but I'll leave this answer here for now in case it is useful.
Related
I am trying to create an array that shows every digit permutation of a given number input. With a given input "123", the array should look like this:
["123", "132", "213", "231", "312", "321"]
I can get an array containing arrays of the separate digits:
a = []
"123".split('').each {|n| a.push(n) }
arraycombinations = a.permutation(a.length).to_a
# => [["1", "2", "3"], ["1", "3", "2"], ["2", "1", "3"], ["2", "3", "1"], ["3", "1", "2"], ["3", "2", "1"]]
but I cannot figure out how to join the second or third dimensions of arraycombinations while preserving the first dimension.
Each of these attempts failed:
arraycombinations.map {|x| print arraycombinations.join("") }
arraycombinations.map {|ar| ar.split(",") }
arraycombinations.each {|index| arraycombinations(index).join("") }
How can I isolate the join function to apply to only the second dimension within a multidimensional array?
Assuming you already have an array of arrays such as
a = [["1","2","3"],["1","3","2"],["2","1","3"],["2","3","1"], ["3","1","2"],["3","2","1"]]
a.map { |i| i.join}
#=>["123", "132", "213", "231", "312", "321"]
It's simple really
"123".split("").permutation.to_a.map { |x| x.join }
Let me explain a bit:
"123".split("") gives you an array ["1","2","3"]
permutation.to_a gives you array of arrays [["1","2","3"], ["2","1","3"] ... ]
then you must join each of those arrays inside with map { |x| x.join }
and you get the required end result.
Like this:
arraycombinations.map(&:join)
# => ["123", "132", "213", "231", "312", "321"]
I've recently solved a problem, which takes a 3-4 digit number, such as 1234, (as well as some greater numbers) and returns a sorted array of ALL the possible permutations of the numbers [1234, 1432, 4213, 2431, 3412, 3214, etc.]
I don't like my solution, because it used .times to add the numbers to the array, and thus is still fallible, and furthermore ugly. Is there a way that the numbers could be added to the array the perfect number of times, so that as soon as all the possible shufflings of the numbers have been reached, the program will stop and return the array?
def number_shuffle(number)
array = []
number = number.to_s.split(//)
1000.times{ array << number.shuffle.join.to_i}
array.uniq.sort
end
Do as below using Array#permutation:
>> a = 1234.to_s.chars
=> ["1", "2", "3", "4"]
>> a.permutation(4).to_a
=> [["1", "2", "3", "4"],
["1", "2", "4", "3"],
["1", "3", "2", "4"],
["1", "3", "4", "2"],
["1", "4", "2", "3"],
["1", "4", "3", "2"],
["2", "1", "3", "4"],
["2", "1", "4", "3"],...]
Your modified method will be :
def number_shuffle(number,size)
number.to_s.chars.permutation(size).to_a
end
For your method it will be:
def number_shuffle(number)
a = number.to_s.chars
a.permutation(a.size).to_a.map { |b| b.join.to_i }
end
p number_shuffle 123 # => [123, 132, 213, 231, 312, 321]
My array is ["Mehmet,1,3,0,0,0\n", "Veli,2,1,2,0,2\n", "Ali,0,1,1,0,0\n"].
I want to declare two dimensional array like array[1][2] with first dimension for name and second one for note.
How can I make it?
Text.txt is
Mehmet,1,3,0,0,0
Veli,2,1,2,0,2
Ali,0,1,1,0,0
My code is
filename = "text.txt"
results = []
File.new(filename, "r").each { |line| results << line }
results.inject([]){|ar,s|
ar.concat(s.split(/,/))}
puts results.inspect
To modify the set that you first posted:
data = ["Mehmet,1,3,0,0,0\n", "Veli,2,1,2,0,2\n", "Ali,0,1,1,0,0\n"]
data = data.map {|x| y = x.split(","); [y.delete_at(0), y] }
=> [["Mehmet", ["1", "3", "0", "0", "0\n"]],
["Veli", ["2", "1", "2", "0", "2\n"]],
["Ali", ["0", "1", "1", "0", "0\n"]]]
puts data[0][0]
=> Mehmet
array = File.read("text.txt").split
# => ["Mehmet,1,3,0,0,0", "Veli,2,1,2,0,2", "Ali,0,1,1,0,0"]
array.map { |ar| x, *xs = ar.split(","); [x, xs.join] }
# => [["Mehmet", "13000"], ["Veli", "21202"], ["Ali", "01100"]]
Or, if you don't want to join the second sub-array
array.map { |ar| x, *xs = ar.split(","); [x, xs] }
# => [["Mehmet", ["1", "3", "0", "0", "0"]],
# ["Veli", ["2", "1", "2", "0", "2"]],
# ["Ali", ["0", "1", "1", "0", "0"]]]
2d array means array of arrays. So, simply it can be like:
board = [ [ 1, 2, 3 ],[ 4, 5, 6 ]]
Are you looking for something like this?
array = ["Mehmet,1,3,0,0,0\n", "Veli,2,1,2,0,2\n", "Ali,0,1,1,0,0\n"]
new_array = array.map do |elem|
splited = elem.split(/[,\s]/)
[splited.shift, splited]
end
# => [["Mehmet", ["1", "3", "0", "0", "0"]],
# ["Veli", ["2", "1", "2", "0", "2"]],
# ["Ali", ["0", "1", "1", "0", "0"]]]
I have a nested array that looks like this:
#nested = [
['1','2','3'],
['1','5','9'],
['1','4','7'],
['3','5','7'],
['3','6','9'],
['7','8','9'],
['4','5','6'],
['2','5','8']
]
I'd like to take a user input of any integer (that 1..9) and find every array that has that input integer.
Not sure how to do it.
Use select:
num_to_search = "9"
#nested.select do |array|
array.include? num_to_search
end
#=> [["1", "5", "9"], ["3", "6", "9"], ["7", "8", "9"]]
I have an array of values, and an array which determines the order.
How can I quickly re-arrange the array in the given order?
data = ['0','1','2','3','4','5']
order = [3,1,2,0,4,5]
I want:
data = ['3','1','2','0','4','5']
You can use the values_at method written for this kind of task:
data = ['0','1','2','3','4','5']
order = [3,1,2,0,4,5]
data.values_at *order
# => ["3", "1", "2", "0", "4", "5"]
data = ["0", "1", "2", "3", "4", "5"]
order = [3, 1, 2, 0, 4, 5]
> order.map{|x| data[x]}
=> ["3", "1", "2", "0", "4", "5"]
If you are not sure if the indices are correct, you can do this:
> order.map{|x| data.fetch(x)} # will raise an exception if index out of bounds
=> ["3", "1", "2", "0", "4", "5"]
Not as good as #Jakub's answer using Array#values_at (which I would argue should be the accepted answer) but here are some other fun alternatives:
p data.sort_by.with_index{ |d,i| order[i] }
p data.zip(order).sort_by(&:last).map(&:first)