ruby - Consolidate nested arrays and erase the subarrays that have been consolidated? -

i'm trying take bunch of number-word pairs , group words according common numbers. can match numbers, merge subarrays share number, , erase first of subarrays. when try delete second, error:

"in block in <main>': undefined method[]' nil:nilclass (nomethoderror)"

the guilty line -- ary.delete_at(i+1) -- has been commented out. secondary problem: mrbtree not taking nested arrays input...

ary = [[2.28, "cat"], [2.28, "bat"], [2.327, "bear"], [2.68, "ant"], [2.68, "anu"]] = 0  in 0 ... ary.size - 1     if ary[i][0] == ary[i+1][0]         b = (ary[i]+ary[i+1]).uniq         ary.delete_at(i)                 # ary.delete_at(i+1)         c = [b.first], b.pop(b.length - 1)         h = hash[*c]         ary.push(*h)         # mrbtree = multirbtree[c]     end end  puts ary.inspect 

output:

# => [ # =>   [2.28, "bat"],  # =>   [2.327, "bear"],  # =>   [2.68, "anu"],  # =>   [ # =>     [2.28], ["cat", "bat"] # =>   ],  # =>   [ # =>     [2.68], ["ant", "anu"] # =>   ] # => ] 

any appreciated!

your attempt failing because modifying array (which has impact on a.size) in loop. loop end condition not adjusted automagically. accessing things have deleted before.

if array not big, do:

p hash[ary.group_by(&:first).map { | k, v | [k, v.map(&:last)] }] # => {2.28=>["cat", "bat"], 2.327=>["bear"], 2.68=>["ant", "anu"]} 

it works way:

ary.group_by(&:first)   # group 2-elem arrays number, creating hash                          #     {2.28=>[[2.28, "cat"], [2.28, "bat"]], ...} .map  { | k, v | ... }  # change array of key-value pairs [k, v.map(&:last)]      # pairs value-array contains strings hash[ ... ]             # make whole thing hash again 

creating intermediate array , transferring hash overhead. if turns out issue, might better:

h = hash.new { | a, k | a[k] = [] }   # hash [] default value p ary.inject(h) { | a, (k, v) | a[k] << v; }