CODEWITHSUNDEEP
ruby
Scott
Scott

Reputation: 1127

Ruby - 2 dimension array search

I have the following 2 dimension array

data = [
 [5014031, nil], [5014032, nil], [5014033, 0], 
 [5014034, nil], [3014035, 1], [5014036, 1], 
 [5014037, 2], [5014038, nil], [5014039, 2], 
 [5014040, nil], [2014041, nil], [3014042, 2]
]

When I know the value of the 1st integer of one of these arrays e.g. 5014034, what would be the most efficient way to gain the next integer value where the 2nd element matches to nil? (e.g. I would expect 5014038 to be returned)

Thanks Scott

Upvotes: 1

Views: 54

Answers (3)

Chris
Chris

Reputation: 36536

Simple way, using #drop_while and #find_index:

data = [
  [5014031, nil], [5014032, nil], [5014033, 0],
  [5014034, nil], [5014035, 1  ], [5014036, 1],
  [5014037, 2  ], [5014038, nil], [5014039, 2],
  [5014040, nil], [5014041, nil], [5014042, 2]
]

remaining_arr = data.drop_while { |arr| arr[0] != 5014034 }[1..]
next_int = remaining_arr[remaining_arr.find_index { |arr| arr[1].nil? }][0]

Alternatively:

data
  .drop_while { |x| x[0] != 5014034 }[1..]
  .drop_while { |x| !x[1].nil? }[0][0]
# => 5014038

Upvotes: 3

Sebastián Palma
Sebastián Palma

Reputation: 33420

You could slice the array into two when the first element in the inner array matches 5014034. Extract the second resulting array and use find to look for the inner array whose second element is nil:

arr
  .slice_when { |a, _| a == 5014034 } # #<Enumerator: ...>
  .to_a                               # [[[5014031, nil], [5014032, nil], [5014033, 0], [5014034, nil]], [[5014035, 1], [5014036, 1], [5014037, 2], [5014038, nil], [5014039, 2], [5014040, nil], [5014041, nil], [5014042, 2]]]
  [1]                                 # [[5014035, 1], [5014036, 1], [5014037, 2], [5014038, nil], [5014039, 2], [5014040, nil], [5014041, nil], [5014042, 2]]
  .find { |_, b| b.nil? }             # [5014038, nil]
  [0]                                 # 5014038

Notice this method chaining might fail if there's no array in arr whose first object inside matches 5014034, and/or the same for find.

Upvotes: 2

Christopher Oezbek
Christopher Oezbek

Reputation: 26353

If sorted then the following might be faster

data = [
 [5014031, nil], [5014032, nil], [5014033, 0], 
 [5014034, nil], [5014035, 1], [5014036, 1], 
 [5014037, 2], [5014038, nil], [5014039, 2], 
 [5014040, nil], [5014041, nil], [5014042, 2]
]

start_element = data.bsearch_index{ |a| a[0] >= 5014034 }

if start_element == nil || data[start_element] != 5014034
  puts "not found"
else
  data.slice((start_element+1)..).find { |a| a[1] == nil }[0]
end

Upvotes: 0

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