Add Josephus Problem in Ruby (#4484)

Author: AAshGray

archive/r/ruby/josephus-problem.rb

@@ -0,0 +1,32 @@
+def josephus_problem(array, k, start)
+    if (array.length == 1)
+      # if the array is one item left, return the survivor value
+      puts array[0]
+    else
+        # set the index position (start + (k - 1)) and set wrap with %
+        index = (start + k - 1)
+        wrap = index % array.length
+        array.delete_at(wrap)
+        return josephus_problem(array, k, wrap)
+    end
+end
+
+def error()
+    puts "Usage: please input the total number of people and number of people to skip."
+end
+
+# check for incorrect number of arguments
+# .any? loops over the elements of ARGV to check if the argument contains non-digit characters or empty strings
+if ARGV.length != 2 || ARGV.any? { |arg| arg.match(/[^0-9]/) || arg.empty? }
+    error()
+else
+    # convert the arguments to integers
+    n = ARGV[0].to_i
+    k = ARGV[1].to_i
+
+    # create an array with a length of argument n
+    array = [*1..n]
+
+    # pass our array to the function with k and our start index (0)
+    josephus_problem(array, k, 0)
+end