From 8c39f11d63d9a696e7b1f0f54fa02d7927b70f0a Mon Sep 17 00:00:00 2001
From: v-log <v-log1313@mail.ru>
Date: Tue, 10 Apr 2018 10:41:45 +0300
Subject: [PATCH] Bottom-up mergesort implementation with tests

---
 RUBY/lib/2_2_merge_sort/merge_sort.rb         | 118 +++++++++++-------
 .../tests/2_2_sort_algs/merge_sort_bu_test.rb |  10 ++
 2 files changed, 83 insertions(+), 45 deletions(-)
 create mode 100644 RUBY/tests/2_2_sort_algs/merge_sort_bu_test.rb

diff --git a/RUBY/lib/2_2_merge_sort/merge_sort.rb b/RUBY/lib/2_2_merge_sort/merge_sort.rb
index 53c4bb6..85f252f 100644
--- a/RUBY/lib/2_2_merge_sort/merge_sort.rb
+++ b/RUBY/lib/2_2_merge_sort/merge_sort.rb
@@ -1,67 +1,95 @@
-def sorted?(a)
-  (0...a.size - 1).all? { |i| a[i] <= a[i + 1] }
-end
+module MergeSort
+  def sorted?(a)
+    (0...a.size - 1).all? { |i| a[i] <= a[i + 1] }
+  end
+
+  def merge_sort!(a, &block)
+    return a if a.size <= 1
+    aux = Array.new(a.size)
 
-def merge_sort!(a, &block)
-  return a if a.size <= 1
-  aux = Array.new(a.size)
-  if block_given?
-    merge_sort_hlpr!(a, 0, a.size - 1, aux, &block)
-  else
-    merge_sort_hlpr!(a, 0, a.size - 1, aux, &Proc.new {|x| x})
+    if block_given?
+      merge_sort_hlpr!(a, 0, a.size - 1, aux, &block)
+    else
+      merge_sort_hlpr!(a, 0, a.size - 1, aux, &Proc.new { |x| x })
+    end
+    a
   end
-  a
-end
 
-private
+  def merge_sort_bu!(a, &block)
+    return a if a.size <= 1
+    n = a.length
+    aux = Array.new(n)
+    sz = 1
 
-def merge_sort_hlpr!(a, lo, hi, aux, &block)
-  if hi <= lo
-    return a
+    while sz < n do
+      0.step(n - sz, 2 * sz) do |lo|
+        hi = less(lo + sz + sz - 1, n - 1)
+        if block_given?
+          merge!(a, lo, lo + sz - 1, hi, aux, &block)
+        else
+          merge!(a, lo, lo + sz - 1, hi, aux) { |x| x }
+        end
+      end      
+      sz += sz
+    end
+    a
   end
 
-  mid = lo + (hi - lo)/2
-  merge_sort_hlpr!(a, lo, mid, aux, &block)
-  merge_sort_hlpr!(a, mid + 1, hi, aux, &block)
-  merge!(a, lo, mid, hi, aux, &block)
-  a
-end
+  private
 
-def merge! (a, lo, mid, hi, aux, &block)
-  i = lo
-  j = mid + 1
-  (lo..hi).each do |x|
-    aux[x] = a[x]
+  def less(a, b)
+    a < b ? a : b
   end
 
-  (lo..hi).each do |x|
-    if i > mid
-      a[x] = aux[j]
-      j += 1
-    elsif j > hi
-      a[x] = aux[i]
-      i += 1
-    elsif block.call(aux[j]) < block.call(aux[i])
-      a[x] = aux[j]
-      j += 1
-    else
-      a[x] = aux[i]
-      i += 1
+  def merge_sort_hlpr!(a, lo, hi, aux, &block)
+    if hi <= lo
+      return a
+    end
+
+    mid = lo + (hi - lo)/2
+    merge_sort_hlpr!(a, lo, mid, aux, &block)
+    merge_sort_hlpr!(a, mid + 1, hi, aux, &block)
+    merge!(a, lo, mid, hi, aux, &block)
+  end
+
+  def merge! (a, lo, mid, hi, aux, &block)
+    i = lo
+    j = mid + 1
+    (lo..hi).each do |x|
+      aux[x] = a[x]
+    end
+
+    (lo..hi).each do |x|
+      if i > mid
+        a[x] = aux[j]
+        j += 1
+      elsif j > hi
+        a[x] = aux[i]
+        i += 1
+      elsif block.call(aux[j]) < block.call(aux[i])
+        a[x] = aux[j]
+        j += 1
+      else
+        a[x] = aux[i]
+        i += 1
+      end
     end
   end
-  a
 end
 
+include MergeSort
+
 a = (0..30).to_a.shuffle
 puts a.inspect
 puts sorted?(a)
-merge_sort!(a)
+#merge_sort!(a)
+merge_sort_bu!(a)
 raise unless sorted?(a)
 puts "result:" + "\n" + a.inspect
-puts sorted?(a).to_s
+puts sorted?(a)
 puts 
 b = [['Vasya', 1], ['Petya', 3], ['Kolya', 2]]
 puts b.inspect
-merge_sort!(b) { |item| -item[1] }
+#merge_sort!(b) { |item| -item[1] }
+merge_sort_bu!(b) { |item| -item[1] }
 puts "result:" + "\n" + b.inspect # [["Petya", 3], ["Kolya", 2], ["Vasya", 1]]
-
diff --git a/RUBY/tests/2_2_sort_algs/merge_sort_bu_test.rb b/RUBY/tests/2_2_sort_algs/merge_sort_bu_test.rb
new file mode 100644
index 0000000..4977dbb
--- /dev/null
+++ b/RUBY/tests/2_2_sort_algs/merge_sort_bu_test.rb
@@ -0,0 +1,10 @@
+require_relative 'sort_test' 
+require_relative '../../lib/2_2_merge_sort/merge_sort'
+
+class MergeSortTest < Minitest::Test
+  include SortTestModule
+  
+  def sort!(a, &block) 
+    merge_sort_bu!(a, &block)
+  end
+end