Merge pull request #20 from tuwukee/master

Add radix sort algorithm

radix_sort.rb

@@ -0,0 +1,25 @@
+# This is a pure ruby implementation of the radix sort algorithm
+# the function returns collection ordered by ascending
+# Example:
+# pry(main)> radix_sort([6, 22, 43, 16, 0, 15, 9])
+# => [0, 6, 9, 15, 16, 22, 43]
+
+def radix_sort(array, base = 10)
+  # passes count equals to the number of digits in the longest number
+  passes = (Math.log(array.minmax.map(&:abs).max) / Math.log(base)).floor + 1
+  passes.times do |i|
+    buckets = Array.new(2 * base) { [] }
+    base_i = base**i
+
+    # elements are added to buckets
+    # according to the current place-value digit
+    array.each do |j|
+      n = (j / base_i) % base
+      n += base if j >= 0
+      buckets[n] << j
+    end
+    array = buckets.flatten
+  end
+
+  array
+end