Question

How to rearrange an array into a zig-zag pattern (a < b > c < d > e < f > g) in Ruby

Answer 1

# This program rearranges an array into a zig-zag pattern, where the elements 
# alternate between being smaller and larger than their neighbors

def rearrange_into_zigzag(arr)
  (0...arr.length - 1).each do |i|
    if i.even?
      # Expect arr[i] < arr[i + 1]
      if arr[i] > arr[i + 1]
        arr[i], arr[i + 1] = arr[i + 1], arr[i]
      end
    else
      # Expect arr[i] > arr[i + 1]
      if arr[i] < arr[i + 1]
        arr[i], arr[i + 1] = arr[i + 1], arr[i]
      end
    end
  end

  arr
end

arr = [3, 5, 1, 7, 9, 6, 4, 2]

rearrange_into_zigzag(arr)

p arr


# run:
#
# [3, 5, 1, 9, 6, 7, 2, 4]
#

 

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