diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index c8a32a4..4fbccbe 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -1,8 +1,23 @@ # This method uses a heap to sort an array. -# Time Complexity: ? -# Space Complexity: ? +# Time Complexity: O(m+n) +# Space Complexity: O(n) - will have a call stack equal to number of nodes, though we are make a constant number of data structures... maybe O(1) def heap_sort(list) - raise NotImplementedError, "Method not implemented yet..." -end \ No newline at end of file + # raise NotImplementedError, "Method not implemented yet..." + # left_child = i * 2 + 1 + # right_child = i * 2 + 2 + heap = MinHeap.new + + list.each do |element| + heap.add(element) + end + + sorted_list = [] + until heap.empty? + sorted_list.push(heap.remove) + end + + return sorted_list + +end \ No newline at end of file diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6eaa630..86f1870 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -14,18 +14,26 @@ def initialize end # This method adds a HeapNode instance to the heap - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: O(m+1), where m is height - O(1) for adding, O(m) for heap up + # Space Complexity: O(1) - no new data structures made, but O(m) for heap up call stack (is it the number of calls in the calls stack or number of structures made?) def add(key, value = key) - raise NotImplementedError, "Method not implemented yet..." + @store << HeapNode.new(key, value) + + if @store.length > 1 + heap_up(@store.length - 1) + end + end # This method removes and returns an element from the heap # maintaining the heap structure - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: O(n+1) + # Space Complexity: O(1) def remove() - raise NotImplementedError, "Method not implemented yet..." + swap(0, -1) + popped = @store.pop + heap_down(0) + return popped.value end @@ -44,10 +52,16 @@ def to_s end # This method returns true if the heap is empty - # Time complexity: ? - # Space complexity: ? + # Time complexity: O(1) + # Space complexity: O(1) def empty? - raise NotImplementedError, "Method not implemented yet..." + + if @store.nil? || @store.length == 0 + return true + else + return false + end + end private @@ -55,20 +69,44 @@ def empty? # This helper method takes an index and # moves it up the heap, if it is less than it's parent node. # It could be **very** helpful for the add method. - # Time complexity: ? - # Space complexity: ? + # Time complexity: O(m) where m is height + # Space complexity: O(1), no persistent data structure is made beyond 1 temporary reassigned variable def heap_up(index) + return if index == 0 + + if @store[index].key < @store[((index - (index % 3)) / 2)].key + temp = @store[index] + @store[index] = @store[((index - (index % 3)) / 2)] + @store[((index - (index % 3)) / 2)] = temp + end + + heap_up(((index - (index % 3)) / 2)) end # This helper method takes an index and # moves it up the heap if it's smaller # than it's parent node. + # left_child = i * 2 + 1 + # right_child = i * 2 + 2 def heap_down(index) - raise NotImplementedError, "Method not implemented yet..." + return if @store[index].nil? + + if !@store[index * 2 + 1].nil? && @store[index].key > @store[index * 2 + 1].key + swap(index, (index * 2 + 1)) + end + + if !@store[index * 2 + 2].nil? && @store[index].key > @store[index * 2 + 2].key + swap(index, (index * 2 + 2)) + end + + heap_down(index * 2 + 1) + heap_down(index * 2 + 2) + end # If you want a swap method... you're welcome + #THANK YOUUUUUU def swap(index_1, index_2) temp = @store[index_1] @store[index_1] = @store[index_2] diff --git a/test/heapsort_test.rb b/test/heapsort_test.rb index 34402ac..271e711 100644 --- a/test/heapsort_test.rb +++ b/test/heapsort_test.rb @@ -1,12 +1,12 @@ require_relative "test_helper" -xdescribe "heapsort" do +describe "heapsort" do it "sorts an empty array" do # Arrange list = [] # Act - result = heapsort(list) + result = heap_sort(list) # Assert expect(result).must_equal [] @@ -17,7 +17,7 @@ list = [5] # Act - result = heapsort(list) + result = heap_sort(list) # Assert expect(result).must_equal [5] @@ -28,7 +28,7 @@ list = [5, 27, 3, 16, -50] # Act - result = heapsort(list) + result = heap_sort(list) # Assert expect(result).must_equal [-50, 3, 5, 16, 27] diff --git a/test/min_heap_test.rb b/test/min_heap_test.rb index 186d4c2..ca4bb35 100644 --- a/test/min_heap_test.rb +++ b/test/min_heap_test.rb @@ -52,30 +52,30 @@ end it "can remove nodes in the proper order" do - # Arrange - heap.add(3, "Pasta") - heap.add(6, "Soup") - heap.add(1, "Pizza") - heap.add(0, "Donuts") - heap.add(16, "Cookies") - heap.add(57, "Cake") + # Arrange + heap.add(3, "Pasta") + heap.add(6, "Soup") + heap.add(1, "Pizza") + heap.add(0, "Donuts") + heap.add(16, "Cookies") + heap.add(57, "Cake") - # Act - removed = heap.remove + # Act + removed = heap.remove - # Assert - expect(removed).must_equal "Donuts" + # Assert + expect(removed).must_equal "Donuts" - # Another Act - removed = heap.remove + # Another Act + removed = heap.remove - # Another assert - expect(removed).must_equal "Pizza" + # Another assert + expect(removed).must_equal "Pizza" - # Another Act - removed = heap.remove + # Another Act + removed = heap.remove - # Another assert - expect(removed).must_equal "Pasta" - end + # Another assert + expect(removed).must_equal "Pasta" + end end \ No newline at end of file