use Forwardable to delegate to Array

- remove CompleteTree#last_idx

Author: rickhull

lib/compsci/complete_tree.rb

@@ -1,11 +1,13 @@
-require 'compsci'
+require 'forwardable'
 
 module CompSci
   # A CompleteTree can very efficiently use an array for storage using
   # simple arithmetic to determine parent child relationships.
   # Any type of value may be stored in the array / tree at any location.
   #
   class CompleteTree
+    extend Forwardable
+
     # given a child index and child count (e.g. 2 for a binary tree)
     # integer math maps several children to one parent index
     def self.parent_idx(idx, n)
@@ -31,26 +33,17 @@ def self.generation(idx, n)
     end
 
     attr_reader :array
+    def_delegators :@array,
+                   :push, :pop, :shift, :unshift,
+                   :size, :count, :first, :last, :[]
 
     def initialize(array: [], child_slots: 2)
       @array = array
       @child_slots = child_slots
     end
 
-    def push val
-      @array.push val
-    end
-
-    def pop
-      @array.pop
-    end
-
-    def size
-      @array.size
-    end
-
-    def last_idx
-      @array.size - 1 unless @array.empty?
+    def swap(idx1, idx2)
+      @array[idx1], @array[idx2] = @array[idx2], @array[idx1]
     end
 
     def display(width: 80)

lib/compsci/heap.rb

@@ -63,7 +63,8 @@ def peek
   # * idx represents the node suspected to violate the heap
   # * intended to be O(log n) on heap size (log base child_slots)
   #
-  def sift_up(idx)
+  def sift_up(idx = nil)
+    idx ||= @array.size - 1
     return self if idx <= 0
     pidx = self.class.parent_idx(idx, @child_slots)
     if !self.heapish?(pidx, idx)
@@ -78,7 +79,8 @@ def sift_up(idx)
   # * intended to be O(log n) on heap size (log base child_slots)
   # * slower than sift_up because one parent vs multiple children
   #
-  def sift_down(idx)
+  def sift_down(idx = nil)
+    idx ||= 0
     return self if idx >= @array.size
     cidxs = self.class.children_idx(idx, @child_slots)
     # promote the heapiest child

test/complete_tree.rb

@@ -124,12 +124,5 @@
       expect(@empty.size).must_equal 0
       expect(@nonempty.size).must_equal @array.size
     end
-
-    it "must have a last_idx, nil when empty" do
-      expect(@empty.last_idx.nil?).must_equal true
-      expect(@nonempty.last_idx).must_equal 99
-    end
-
-    # TODO: push, pop, display
   end
 end

test/heap.rb

@@ -26,7 +26,7 @@
 
       @maxheap.array.push 10
       expect(@maxheap.heap?).must_equal false
-      @maxheap.sift_up @maxheap.last_idx
+      @maxheap.sift_up
       expect(@maxheap.heap?).must_equal true
     end
 
@@ -68,7 +68,7 @@
 
       @minheap.array.push 0
       expect(@minheap.heap?).must_equal false
-      @minheap.sift_up @minheap.last_idx
+      @minheap.sift_up
       expect(@minheap.heap?).must_equal true
     end
 
@@ -111,7 +111,7 @@
 
       @heap3.array.push 10
       expect(@heap3.heap?).must_equal false
-      @heap3.sift_up @heap3.last_idx
+      @heap3.sift_up
       expect(@heap3.heap?).must_equal true
     end