Generate random number using LCG.

Author: deepakhb2

Problems/generate_random_number.rb

@@ -0,0 +1,47 @@
+# ref: https://rosettacode.org/wiki/Linear_congruential_generator
+# Linear congruential generator Rn+1 = A * Rn + C (mod M)
+
+module LCG
+  module Common
+    # The original seed of this generator.
+    attr_reader :seed
+ 
+    # Creates a linear congruential generator with the given _seed_.
+    def initialize(seed)
+      @seed = @r = seed
+    end
+  end
+ 
+  # LCG::Berkeley generates 31-bit integers using the same formula
+  # as BSD rand().
+  class Berkeley
+    include Common
+    def rand
+      @r = (1103515245 * @r + 12345) % 0x7fff_ffff
+    end
+  end
+ 
+  # LCG::Microsoft generates 15-bit integers using the same formula
+  # as rand() from the Microsoft C Runtime.
+  class Microsoft
+    include Common
+    def rand
+      @r = (214013 * @r + 2531011) % 0x7fff_ffff
+      @r >> 16
+    end
+  end
+end
+
+@random = LCG::Microsoft.new(Time.now.to_i) 
+def rand5
+  @random.rand % 5
+end
+
+p [rand5, rand5, rand5, rand5]
+
+def rand7
+  @random.rand % 7
+end
+
+p [rand7, rand7, rand7, rand7]
+p [rand(7), rand(7), rand(7), rand(7)]