find the 3 numbers that sum to a target number.

find_3_Numbers_that_sum_to_target_number.rb

# Given an array of integers, find the 3 numbers that sum up to a target number.
# ruby find_3_Numbers_that_sum_to_target_number.rb
# Enter the size of array : 5
# Enter 1 element : 
# 1
# Enter 2 element :
# 2
# Enter 3 element :
# 3
# Enter 4 element :
# 4
# Enter 5 element :
# 5
# Enter the target number : 12
# Triplet is : 3, 4, 5

class FindTripletNumbersThatSumToTargetNumber
  def initialize
    p "Enter the size of array :"
    array_size = gets.strip.to_i
    if array_size < 3
      puts "Array size should be greater than 3"
    else
      array = []
      for i in (0..array_size-1)
          p "Enter #{i+1} element :"
          array[i] = gets.strip.to_i
      end
      p "Enter the target number :"
      target_number = gets.strip.to_i
      merge_sort array
      find_3_Numbers_that_sum_to_target_number(array, array_size, target_number)
    end
  end

  def merge_sort(array)
  	n = array.length
  	if n > 1
  		mid = n/2
  		lefthalf = array[0..mid-1]
  		righthalf = array[mid..n-1]
  		merge_sort lefthalf
  		merge_sort righthalf
  		i = j = k = 0
  		while i < lefthalf.length and j < righthalf.length
  			if lefthalf[i] < righthalf[j]
  				array[k] = lefthalf[i]
  				i = i+1
  			else
  				array[k] = righthalf[j]
  				j = j+1
  			end
  			k += 1
  		end

  		while i < lefthalf.length
  			array[k] = lefthalf[i]
  			i = i+1
  			k = k+1
  		end

  		while j < righthalf.length
  			array[k] = righthalf[j]
  			j = j+1
  			k = k+1
  		end
  	end
  end

  def find_3_Numbers_that_sum_to_target_number(array, array_size, target_number)
    for i in 0..array_size-2
      j = i+1
      k = array_size-1
      for j in j..array_size-2
        while j < k
          if array[i] + array[j] + array[k] == target_number
            puts "Triplet is : #{array[i]}, #{array[j]}, #{array[k]}"
            return true
          elsif
            array[i] + array[j] + array[k] < target_number
            j += 1
          elsif array[i] + array[j] + array[k] > target_number
            k += 1
          end
        end
      end
    end
    puts "Triplet doesn't exist"
    return false
  end
end
number = FindTripletNumbersThatSumToTargetNumber.new