From f10baef1a1dddfdaff07e68ab3cd4ed06a87d0e2 Mon Sep 17 00:00:00 2001 From: Stephanie Date: Sun, 3 Jan 2021 20:41:11 -0800 Subject: [PATCH 1/3] heap sort complete) --- lib/heap_sort.rb | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index 6b692e4..7971603 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -1,8 +1,23 @@ - +# require_relative "min_heap" # This method uses a heap to sort an array. -# Time Complexity: ? -# Space Complexity: ? +# Time Complexity: O(nlogn) +# Space Complexity: O(nlogn) def heapsort(list) - raise NotImplementedError, "Method not implemented yet..." + + return list if list.length - 1 <= 1 + + heap = MinHeap.new + + list.each do |value| + heap.add(value) + end + + result = [] + + list.length.times do + result << heap.remove.value + end + + return result end \ No newline at end of file From 145983af74f130d81cbfb5231dbed4d90fecdbaa Mon Sep 17 00:00:00 2001 From: Stephanie Date: Sun, 3 Jan 2021 20:42:02 -0800 Subject: [PATCH 2/3] min heap incomplete --- lib/min_heap.rb | 46 +++++++++++++++++++++++++++++++++++++++------- 1 file changed, 39 insertions(+), 7 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6eaa630..dd6a074 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -14,10 +14,11 @@ def initialize end # This method adds a HeapNode instance to the heap - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: O(logn) + # Space Complexity: O(1) def add(key, value = key) - raise NotImplementedError, "Method not implemented yet..." + @store << HeapNode.new(key, value) + heap_up(@store.length - 1) end # This method removes and returns an element from the heap @@ -25,7 +26,14 @@ def add(key, value = key) # Time Complexity: ? # Space Complexity: ? def remove() - raise NotImplementedError, "Method not implemented yet..." + return nil if @store.empty? + + swap(0, @store.length - 1) + result = @store.pop + heap_down(0) + return result + + end @@ -47,7 +55,7 @@ def to_s # Time complexity: ? # Space complexity: ? def empty? - raise NotImplementedError, "Method not implemented yet..." + return if @store.empty? end private @@ -58,14 +66,38 @@ def empty? # Time complexity: ? # Space complexity: ? def heap_up(index) - + return if index == 0 + parent_index = (index - 1) / 2 + if @store[parent_index].key > @store[index].key + swap(index, parent_index) + heap_up(parent_index) + end end # This helper method takes an index and # moves it up the heap if it's smaller # than it's parent node. def heap_down(index) - raise NotImplementedError, "Method not implemented yet..." + return if index >= @store.length - 1 + + left_index = index * 2 + 1 + right_index = index * 2 + 2 + + return if !@store[left_index] && !@store[right_index] + + smallest = left_index + + if left_index + if (right_index < @store.length) && (@store[right_index].key < @store[left_index].key) + smallest = right_index + end + + if @store[smallest].key < @store[index].key + swap(index, smallest) + end + heap_down(smallest) + end + end # If you want a swap method... you're welcome From 7e21cb6462fd49d4ca826bd0ea1cfee942f61922 Mon Sep 17 00:00:00 2001 From: Stephanie Date: Sun, 3 Jan 2021 21:52:12 -0800 Subject: [PATCH 3/3] bug fix --- lib/heap_sort.rb | 4 ++-- lib/min_heap.rb | 10 +++++----- test/heapsort_test.rb | 2 +- test/min_heap_test.rb | 30 +++++++++++++++--------------- 4 files changed, 23 insertions(+), 23 deletions(-) diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index 7971603..81316de 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -2,7 +2,7 @@ # This method uses a heap to sort an array. # Time Complexity: O(nlogn) -# Space Complexity: O(nlogn) +# Space Complexity: O(1) def heapsort(list) return list if list.length - 1 <= 1 @@ -16,7 +16,7 @@ def heapsort(list) result = [] list.length.times do - result << heap.remove.value + result << heap.remove end return result diff --git a/lib/min_heap.rb b/lib/min_heap.rb index dd6a074..ec0b131 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -31,7 +31,7 @@ def remove() swap(0, @store.length - 1) result = @store.pop heap_down(0) - return result + return result.value end @@ -52,8 +52,8 @@ 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? return if @store.empty? end @@ -63,8 +63,8 @@ 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(logn) + # Space complexity: O(1) def heap_up(index) return if index == 0 parent_index = (index - 1) / 2 diff --git a/test/heapsort_test.rb b/test/heapsort_test.rb index 34402ac..7ce79b7 100644 --- a/test/heapsort_test.rb +++ b/test/heapsort_test.rb @@ -1,6 +1,6 @@ require_relative "test_helper" -xdescribe "heapsort" do +describe "heapsort" do it "sorts an empty array" do # Arrange list = [] diff --git a/test/min_heap_test.rb b/test/min_heap_test.rb index 186d4c2..d66da01 100644 --- a/test/min_heap_test.rb +++ b/test/min_heap_test.rb @@ -52,25 +52,25 @@ 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