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Enumerable#min

Updated March 31, 2026 · Enumerable
ruby enumerable min minimum stdlib

Enumerable#min

The min method returns the smallest element in an enumerable collection. It compares elements using the <=> operator (spaceship operator) to determine order.

Basic Usage

Without arguments, min returns the single smallest element:

[3, 1, 4, 1, 5, 9, 2, 6].min
# => 1

["banana", "apple", "cherry"].min
# => "apple"

Getting the N Smallest Elements

Pass an integer n to get the n smallest elements as an array:

[3, 1, 4, 1, 5, 9, 2, 6].min(3)
# => [1, 1, 2]

["banana", "apple", "cherry", "date"].min(2)
# => ["apple", "banana"]

Custom Comparison with a Block

You can provide a block to define custom comparison logic:

[-5, 3, -1, 7, -2].min { |a, b| a.abs <=> b.abs }
# => -1

["hello", "world", "ruby"].min { |a, b| a.length <=> b.length }
# => "ruby"

The block must return -1, 0, or 1 (using the spaceship operator convention).

Handling Empty Collections

min returns nil when called on an empty collection:

[].min
# => nil

[].min(2)
# => []

min vs min_by

These two methods are often confused but behave differently:

MethodWhat it compares
minCompares elements by their actual value using <=>
min_byCompares elements by the result of the block
[1, 2, 3].min
# => 1# min_by compares by block result
["one", "two", "three"].min_by { |s| s.length }
# => "one"

Practical Examples

Finding the Lowest Price

products = [
  { name: "Widget", price: 29.99 },
  { name: "Gadget", price: 49.99 },
  { name: "Doohickey", price: 19.99 }
]

cheapest = products.min { |a, b| a[:price] <=> b[:price] }
cheapest[:name]
# => "Doohickey"

Finding the Smallest String

words = ["elephant", "cat", "giraffe", "ant"]

shortest = words.min { |a, b| a.length <=> b.length }
# => "cat"

Getting the N Cheapest Items

products = [
  { name: "Widget", price: 29.99 },
  { name: "Gadget", price: 49.99 },
  { name: "Doohickey", price: 19.99 },
  { name: "Thingamajig", price: 39.99 }
]

products.min(2) { |a, b| a[:price] <=> b[:price] }
# => [{:name=>"Doohickey", :price=>19.99}, {:name=>"Widget", :price=>29.99}]

Working with Custom Objects

class Player
  attr_reader :score

  def initialize(name, score)
    @name = name
    @score = score
  end

  def <=>(other)
    @score <=> other.score
  end

  def to_s
    @name
  end
end

players = [
  Player.new("Alice", 95),
  Player.new("Bob", 87),
  Player.new("Charlie", 92)
]

players.min
# => Bob (score: 87)

Performance Notes

min uses the <=> operator to compare elements. For arrays, it performs a single pass through the collection — O(n) time complexity.

When using min with a block, the comparison logic runs multiple times during the sort. For finding a single minimum, min_by is often more efficient since it only evaluates the block once per element.

See Also