chore: refactor intersection method

lib/day24.rb

@@ -1,33 +1,39 @@
 # frozen_string_literal: true
-#
-class Line
-  attr_reader :slope, :y_intercept
 
-  def initialize(x, y, z, cx, cy, cz)
-    # Calculate the slope
-    @slope = cy.to_f / cx if cx != 0
-    @slope ||= Float::INFINITY # Vertical line
+class Line
+  attr_reader :slope, :y_intercept, :x, :y
 
-    # Calculate the y-intercept
-    if @slope == Float::INFINITY
+  def initialize(x, y, cx, cy)
+    @x = x
+    @y = y
+    if cx == 0
+      @slope = Float::INFINITY
       @x_intercept = x
     else
+      @slope = cy.to_f / cx
       @y_intercept = y - @slope * x
     end
   end
 
   def intersects_with?(other_line)
-    # If slopes are equal, lines are parallel (or identical)
-    return false if @slope == other_line.slope
-
+    return false if @slope == other_line.slope && @slope != Float::INFINITY
+    return false if @slope == Float::INFINITY && other_line.slope == Float::INFINITY && @x_intercept != other_line.x_intercept
     true
   end
 
   def intersection_point(other_line)
-    return nil unless intersects_with?(other_line)
+    return [0, 0] unless intersects_with?(other_line)
 
-    x = (other_line.y_intercept - @y_intercept) / (@slope - other_line.slope)
-    y = @slope * x + @y_intercept
+    if @slope == Float::INFINITY
+      x = @x_intercept
+      y = other_line.slope * x + other_line.y_intercept
+    elsif other_line.slope == Float::INFINITY
+      x = other_line.x_intercept
+      y = @slope * x + @y_intercept
+    else
+      x = (other_line.y_intercept - @y_intercept) / (@slope - other_line.slope)
+      y = @slope * x + @y_intercept
+    end
 
     [x, y]
   end
@@ -39,24 +45,48 @@ def to_s
       "y = #{@slope}x + #{@y_intercept}"
     end
   end
+
+  protected
+
+  def x_intercept
+    @x_intercept
+  end
 end
 
 # Day24
 class Day24
-  def load(file)
+  def load(file, min, max)
     content = File.read(file)
+    @min = min
+    @max = max
     @parts = []
     content.split("\n").each do |line|
       f, e = line.split("@")
       fs = f.split(",").map(&:to_i)
       es = e.split(",").map(&:to_i)
-      @parts << Line.new(fs[0], fs[1], fs[2], es[0], es[1], es[2])
+      @parts << Line.new(fs[0], fs[1], es[0], es[1])
     end
   end
 
   def part1
-    puts @parts[0].intersection_point(@parts[1])
-    sum = 0
-    sum
+    result = []
+    @parts.each_with_index do |part, i|
+      for j in (i + 1)..(@parts.length - 1)
+        other_part = @parts[j]
+
+        if part.intersects_with?(other_part)
+          x, y = part.intersection_point(other_part)
+          # check if the intersection point is in the test grid
+          if x.between?(@min, @max) && y.between?(@min, @max)
+            # check if the intersection point is in the future
+            if x > part.x 
+              puts "Intersection point: #{x}, #{y}"
+              result << part.intersection_point(other_part)
+            end
+          end
+        end
+      end
+    end
+    result.length
   end
 end

test/unit/day24_test.rb

@@ -4,7 +4,13 @@
 class Day24Test < Minitest::Test
   def test_day24a
     sut = Day24.new
-    sut.load('data/day24a.txt')
+    sut.load('data/day24a.txt', 7, 27)
     assert_equal(2, sut.part1)
   end
+
+  def _test_day24
+    sut = Day24.new
+    sut.load('data/day24.txt', 200000000000000, 400000000000000)
+    assert_equal(14472, sut.part1) # too low
+  end
 end