Data commit

Task/Sorting-algorithms-Merge-sort/Ruby/sorting-algorithms-merge-sort-1.rb

@@ -0,0 +1,19 @@
+def merge_sort(m)
+  return m if m.length <= 1
+
+  middle = m.length / 2
+  left = merge_sort(m[0...middle])
+  right = merge_sort(m[middle..-1])
+  merge(left, right)
+end
+
+def merge(left, right)
+  result = []
+  until left.empty? || right.empty?
+    result << (left.first<=right.first ? left.shift : right.shift)
+  end
+  result + left + right
+end
+
+ary = [7,6,5,9,8,4,3,1,2,0]
+p merge_sort(ary)                  # => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Task/Sorting-algorithms-Merge-sort/Ruby/sorting-algorithms-merge-sort-2.rb

@@ -0,0 +1,34 @@
+class Array
+  def mergesort(&comparitor)
+    return self if length <= 1
+    comparitor ||= proc{|a, b| a <=> b}
+    middle = length / 2
+    left  = self[0...middle].mergesort(&comparitor)
+    right = self[middle..-1].mergesort(&comparitor)
+    merge(left, right, comparitor)
+  end
+
+  private
+  def merge(left, right, comparitor)
+    result = []
+    until left.empty? || right.empty?
+      # change the direction of this comparison to change the direction of the sort
+      if comparitor[left.first, right.first] <= 0
+        result << left.shift
+      else
+        result << right.shift
+      end
+    end
+    result + left + right
+  end
+end
+
+ary = [7,6,5,9,8,4,3,1,2,0]
+p ary.mergesort                    # => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+p ary.mergesort {|a, b| b <=> a}   # => [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
+
+ary = [["UK", "London"], ["US", "New York"], ["US", "Birmingham"], ["UK", "Birmingham"]]
+p ary.mergesort
+# => [["UK", "Birmingham"], ["UK", "London"], ["US", "Birmingham"], ["US", "New York"]]
+p ary.mergesort {|a, b| a[1] <=> b[1]}
+# => [["US", "Birmingham"], ["UK", "Birmingham"], ["UK", "London"], ["US", "New York"]]