Quick union: improve performance using size array.

Author: deepakhb2

Diff for: union-find/weighted-quick-union/solution.rb

@@ -0,0 +1,40 @@
+class WeightedQU
+  attr_reader :size, :values, :sizes
+
+  def initialize(size)
+    @size = size
+    @values = Array.new(@size)
+    @sizes = Array.new(@size)
+    (0...@size).each do |i|
+      @values[i] = i
+    end
+    (0...@size).each do |i|
+      @sizes[i] = 1
+    end
+  end
+
+  def root(p)
+    root = p
+    while(root != @values[root])
+      root = @values[root]
+    end
+    root
+  end
+
+  def connected(p, q)
+    return root(p) == root(q)
+  end
+
+  def union(p, q)
+    pr = root(p)
+    qr = root(q)
+    return if pr == qr
+    if(@sizes[pr] >= @sizes[qr])
+      @values[qr] = pr 
+      @sizes[pr] += @sizes[qr]
+    else
+      @values[pr] = qr 
+      @sizes[qr] += @sizes[pr]
+    end
+  end
+end

Diff for: union-find/weighted-quick-union/spec.rb

@@ -0,0 +1,42 @@
+require_relative './solution.rb'
+
+RSpec.describe WeightedQU do
+  let(:wquick_union) { WeightedQU.new(10)}
+
+  it "Test the values assigned" do
+    expect(wquick_union.size).to eq(10)
+    expect(wquick_union.values.size).to eq(10)
+    expect(wquick_union.sizes.size).to eq(10)
+  end
+
+  it "Check if two elements are connected" do
+    expect(wquick_union.connected(0, 1)).to eq(false)
+  end
+
+  it "Test the algorithm" do
+    wquick_union.union(4, 3)
+    expect(wquick_union.values).to eq([0, 1, 2, 4, 4, 5, 6, 7, 8, 9])
+    wquick_union.union(9, 8)
+    expect(wquick_union.values).to eq([0, 1, 2, 4, 4, 5, 6, 7, 9, 9])
+    wquick_union.union(9, 7)
+    expect(wquick_union.values).to eq([0, 1, 2, 4, 4, 5, 6, 9, 9, 9])
+    wquick_union.union(3, 7)
+    expect(wquick_union.values).to eq([0, 1, 2, 4, 9, 5, 6, 9, 9, 9])
+    wquick_union.union(6, 7)
+    expect(wquick_union.values).to eq([0, 1, 2, 4, 9, 5, 9, 9, 9, 9])
+
+    expect(wquick_union.sizes[9]).to eq(6)
+  end
+
+  it "Get the root element of an element" do
+    wquick_union.union(6, 7)
+    expect(wquick_union.root(7)).to eq(6)
+  end
+
+  it "Check if two elements are connected" do
+    wquick_union.union(0, 1)
+    wquick_union.union(1, 2)
+    wquick_union.union(2, 3)
+    expect(wquick_union.connected(0, 3)).to eq(true)
+  end
+end