Question

How to find the minimum distance between two numbers in an array with Ruby

Answer 1

# Finds the minimum distance between two values in an array.
#
# @param numbers [Array<Integer>] The array to search.
# @param target1 [Integer] The first target value.
# @param target2 [Integer] The second target value.
#
# @return [Integer]
#   The minimum distance between the target values,
#   or -1 if no valid pair exists.
#
# Time Complexity: O(n)
# Space Complexity: O(1)
def find_minimum_distance(numbers, target1, target2)
  raise ArgumentError, "numbers cannot be nil" if numbers.nil?

  # Special case: both targets are the same value.
  return find_minimum_distance_between_duplicates(numbers, target1) if target1 == target2

  last_seen_index = nil
  min_distance = nil

  numbers.each_with_index do |current_value, current_index|
    # Ignore values that are not targets.
    next unless current_value == target1 || current_value == target2

    # If we previously saw the other target value,
    # update the minimum distance.
    unless last_seen_index.nil?
      if current_value != numbers[last_seen_index]
        distance = current_index - last_seen_index

        min_distance =
          min_distance.nil? ? distance : [min_distance, distance].min
      end
    end

    # Remember the most recent occurrence.
    last_seen_index = current_index
  end

  min_distance || -1
end

# Finds the minimum distance between consecutive occurrences
# of the same value.
#
# @param numbers [Array<Integer>] The array to search.
# @param target [Integer] The target value.
#
# @return [Integer]
#   The minimum distance between occurrences,
#   or -1 if fewer than two occurrences exist.
def find_minimum_distance_between_duplicates(numbers, target)
  previous_index = nil
  min_distance = nil

  numbers.each_with_index do |value, index|
    next unless value == target

    unless previous_index.nil? distance = index - previous_index

      min_distance = min_distance.nil? ? distance : [min_distance, distance].min
    end

    previous_index = index
  end

  min_distance || -1
end

# Example usage
numbers = [2, 3, 7, 3, 3, 4, 8, 8, 8, 11, 9, 1, 3]

result = find_minimum_distance(numbers, 3, 8)

if result >= 0
  puts "Minimum distance between 3 and 8: #{result}"
else
  puts "No valid pair found."
end


# run:
#
# Minimum distance between 3 and 8: 2
#

 

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Answer 2

# Finds the minimum distance between two values in an array.
#
def find_minimum_distance(numbers, target1, target2)
  return find_minimum_distance_between_duplicates(numbers, target1) if target1 == target2

  last_index = nil
  last_value = nil
  min_distance = nil

  numbers.each_with_index do |value, index|
    next unless value == target1 || value == target2

    if !last_index.nil? && value != last_value
      distance = index - last_index
      min_distance = min_distance.nil? ? distance : [min_distance, distance].min
    end

    last_index = index
    last_value = value
  end

  min_distance || -1
end

# Example usage
numbers = [2, 3, 7, 3, 3, 4, 8, 8, 8, 11, 9, 1, 3]

result = find_minimum_distance(numbers, 3, 8)

if result >= 0
  puts "Minimum distance between 3 and 8: #{result}"
else
  puts "No valid pair found."
end


# run:
#
# Minimum distance between 3 and 8: 2
#

 

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