yovasx2 · March 23, 2017 01:19
diff --git a/boomerang_constellations.rb b/boomerang_constellations.rb
 #!usr/bin/ruby

 # The night sky can be modeled as an infinite 2D plane. There are N stars at distinct positions on this plane, the ith of which is at coordinates (Xi, Yi).

 # A boomerang constellation is a pair of distinct equal-length line segments which share a single endpoint, such that both endpoints of each segment coincide with a star's location.

 # Two boomerang constellations are distinct if they're not made up of the same unordered pair of line segments. How many distinct boomerang constellations can you spot?

 # Input Format

 # Input begins with an integer N. Then, N lines follow, the ith of which contains the space-separated integers Xi and Yi.

 # Constraints

 # 1 ≤ N ≤ 2,000 
 # -10,000 ≤ Xi, Yi ≤ 10,000 

 # Output Format

 # print the number of boomerang constellations in the night sky.

 # Example 1:

 # Input: 
 # 3 
 # 0 0 
 # 0 1 
 # 0 3 

 # Expected Output: 
 # 0 

 # Explanation: Every pair of stars is a unique distance apart, so there are no boomerang constellations.

 # Example 2:

 # Input: 5 
 # 0 0 
 # 0 1 
 # 0 2 
 # 0 3 
 # 0 4 

 # Expected Output: 4 

 # Explanation: There are 4 boomerang constellations. One of them consists of the line segments (0,0)-(0,2) and (0,2)-(0,4).

 # Sample Input 0

 # 3
 # 0 0
 # 0 1
 # 0 3
 # Sample Output 0

 # 0
 # Sample Input 1

 # 5
 # 0 0
 # 0 1
 # 0 2
 # 0 3
 # 0 4
 # Sample Output 1

 # 4
 # Sample Input 2

 # 4
 # 0 0
 # 0 100
 # 100 0
 # 100 100
 # Sample Output 2

 # 4
 # Sample Input 3

 # 4
 # 0 0
 # -3 4
 # 0 5
 # -5 0
 # Sample Output 3

 # 3
 # Sample Input 4

 # 6
 # 5 6
 # 6 5
 # 7 6
 # 6 7
 # 7 8
 # 8 7
 # Sample Output 4

 # 12

 class Boomerang
  attr_accessor :num_stars, :stars

  def initialize
    @stars = []
    @num_stars = gets.chop.to_i
    for i in 1..@num_stars
      coordinates = clean_params(gets, ' ')
      @stars << Star.new(coordinates[0].to_i, coordinates[1].to_i)
    end
  end

  def clean_params(str, separator = '')
    str.chop.split(separator)
  end

  def dist2(i, j)
    dx2 = (@stars[i].x - @stars[j].x) * (@stars[i].x - @stars[j].x)
    dy2 = (@stars[i].y - @stars[j].y) * (@stars[i].y - @stars[j].y)
    dx2 + dy2
  end

  def num_constellations
    res = 0
    for i in 0..@num_stars-1 do
      distances = {}
      for j in 0..@num_stars-1 do
        if(i!=j)
          d = dist2(i,j)
          distances[d] = 0 unless distances.has_key?(d)
          res += distances[d]
          distances[d]+=1
        end
      end
    end
    res
  end
 end

 class Star
  attr_accessor :x, :y

  def initialize(x, y)
    @x = x
    @y = y
  end
 end

 b = Boomerang.new
 puts b.num_constellations
	#!usr/bin/ruby

	# The night sky can be modeled as an infinite 2D plane. There are N stars at distinct positions on this plane, the ith of which is at coordinates (Xi, Yi).

	# A boomerang constellation is a pair of distinct equal-length line segments which share a single endpoint, such that both endpoints of each segment coincide with a star's location.

	# Two boomerang constellations are distinct if they're not made up of the same unordered pair of line segments. How many distinct boomerang constellations can you spot?

	# Input Format

	# Input begins with an integer N. Then, N lines follow, the ith of which contains the space-separated integers Xi and Yi.

	# Constraints

	# 1 ≤ N ≤ 2,000
	# -10,000 ≤ Xi, Yi ≤ 10,000

	# Output Format

	# print the number of boomerang constellations in the night sky.

	# Example 1:

	# Input:
	# 3
	# 0 0
	# 0 1
	# 0 3

	# Expected Output:
	# 0

	# Explanation: Every pair of stars is a unique distance apart, so there are no boomerang constellations.

	# Example 2:

	# Input: 5
	# 0 0
	# 0 1
	# 0 2
	# 0 3
	# 0 4

	# Expected Output: 4

	# Explanation: There are 4 boomerang constellations. One of them consists of the line segments (0,0)-(0,2) and (0,2)-(0,4).

	# Sample Input 0

	# 3
	# 0 0
	# 0 1
	# 0 3
	# Sample Output 0

	# 0
	# Sample Input 1

	# 5
	# 0 0
	# 0 1
	# 0 2
	# 0 3
	# 0 4
	# Sample Output 1

	# 4
	# Sample Input 2

	# 4
	# 0 0
	# 0 100
	# 100 0
	# 100 100
	# Sample Output 2

	# 4
	# Sample Input 3

	# 4
	# 0 0
	# -3 4
	# 0 5
	# -5 0
	# Sample Output 3

	# 3
	# Sample Input 4

	# 6
	# 5 6
	# 6 5
	# 7 6
	# 6 7
	# 7 8
	# 8 7
	# Sample Output 4

	# 12

	class Boomerang
	attr_accessor :num_stars, :stars

	def initialize
	@stars = []
	@num_stars = gets.chop.to_i
	for i in 1..@num_stars
	coordinates = clean_params(gets, ' ')
	@stars << Star.new(coordinates[0].to_i, coordinates[1].to_i)
	end
	end

	def clean_params(str, separator = '')
	str.chop.split(separator)
	end

	def dist2(i, j)
	dx2 = (@stars[i].x - @stars[j].x) * (@stars[i].x - @stars[j].x)
	dy2 = (@stars[i].y - @stars[j].y) * (@stars[i].y - @stars[j].y)
	dx2 + dy2
	end

	def num_constellations
	res = 0
	for i in 0..@num_stars-1 do
	distances = {}
	for j in 0..@num_stars-1 do
	if(i!=j)
	d = dist2(i,j)
	distances[d] = 0 unless distances.has_key?(d)
	res += distances[d]
	distances[d]+=1
	end
	end
	end
	res
	end
	end

	class Star
	attr_accessor :x, :y

	def initialize(x, y)
	@x = x
	@y = y
	end
	end

	b = Boomerang.new
	puts b.num_constellations