How to find a specific value in a nested array? - arrays

Question

I'm trying to figure out how to place a value into one of three arrays and then shuffle those arrays and have the program output the index location of the value.
Here is what I have so far:
# The purpose of this program is to randomly place the name Zac
# in one of three arrays and return the array number and position of
# Zac
A1 = ["John","Steve","Frank","Charles"]
A2 = ["Sam","Clint","Stuart","James"]
A3 = ["Vic","Jim","Bill","David"]
n = [A1,A2,A3]
name = "Zac"
def placename(title, namelist)
mix = rand(2)
namelist[mix] << title
namelist.shuffle
return namelist
end
allnames = [] << placename(name, n)
def findname(allnames, key)
allnames.each do |i|
until allnames[i].include?(key) == true
i+=1
end
location = allnames[i].find_index(key)
puts "The location and value of #{key} is #{location}"
end
end
findname(allnames, name)
At the moment I'm getting a "undefined method for Nil Class" error (no method error)
Can someone please clarify what I'm doing wrong with this or if there is a more effective way of going about this? Thanks in advance!!

Answer 1

Your approach assumes that in the block starting...
allnames.each do |i|
... that i will contain the index of the allnames element. This isn't true. i will contain the VALUE (contents) of the element.
What you could try as an alternative is...
allnames.each_with_index do |_value, i|
or, you can do...
allnames.each do |value|
and then replace all references to allnames[i] with value
another problem is that...
allnames = [] << placename(name, n)
puts the returned array of arrays inside ANOTHER array. I think what you want to do is..
allnames = placename(name, n)

Answer 2

I modified the last fewlines. I hope this is what you wanted
allnames = placename(name, n)
def findname allnames, key
r = allnames.map.with_index{|x,i|x.include?(key) ? i : p}-[p]
puts "The location of value #{key} is array number #{r[0]} and item number #{allnames[r[0]].index(key)}"
end
findname(allnames, name)
Edit: Randomization
To get randomized array number and item number you have to do the following
def placename(title, namelist)
mix = rand(3) # Since the number of arrays (nested within) is 3 we can use 3 instead of 2
namelist[mix] << title
namelist.map!{|x|x.shuffle}.shuffle! # Shuffling each item and the whole array in place.
return namelist
end

Answer 3

Assuming you want to modify the array in place, I'd do it like this:
# insert name into random subarray
def insert_name name
subarray_idx = rand #name_arrays.size
subarray = #name_arrays[subarray_idx]
insertion_idx = rand subarray.size
#name_arrays[subarray_idx].insert insertion_idx, name
sprintf '"%s" inserted at #name_arrays[%d][%d]',
name, subarray_idx, insertion_idx
end
# define starting array, then print & return the
# message for further parsing if needed
#name_arrays = [
%w[John Steve Frank Charles],
%w[Sam Clint Stuart James],
%w[Vic Jim Bill David],
]
p(insert_name 'Zac')
This has a few benefits:
You can inspect #name_arrays to validate that things look the way you expect.
The message can be parsed with String#scan if desired.
You can modify #insert_name to return your indexes, rather than having to search for the name directly.
If you don't capture the insertion index as a return value, or don't want to parse it from your message String, you can search for it by leveraging Enumerable#each_with_index and Array#index. For example:
# for demonstration only, set this so you can get the same
# results since the insertion index was randomized
#name_arrays =
[["John", "Steve", "Frank", "Charles"],
["Sam", "Clint", "Stuart", "James"],
["Vic", "Jim", "Zac", "Bill", "David"]]
# return indices of nested match
def find_name_idx name
#name_arrays.each_with_index
.map { [_2, _1.index(name)] }
.reject { _1.any? nil }
.pop
end
# use Array#dig to retrieve item at nested index
#name_arrays.dig *find_name_idx('Zac')