From 2e332a7988c400f001599929a59e247065a04945 Mon Sep 17 00:00:00 2001 From: Faiza Ahsan Date: Sun, 22 Sep 2019 12:21:16 -0700 Subject: [PATCH 1/3] Added code for min_heap with all tests passing --- lib/min_heap.rb | 48 +++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 41 insertions(+), 7 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6eaa630..04fe4e1 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -17,7 +17,9 @@ def initialize # Time Complexity: ? # Space Complexity: ? def add(key, value = key) - raise NotImplementedError, "Method not implemented yet..." + heap_node = HeapNode.new(key, value) + @store.push(heap_node) + heap_up(@store.length - 1) end # This method removes and returns an element from the heap @@ -25,7 +27,10 @@ def add(key, value = key) # Time Complexity: ? # Space Complexity: ? def remove() - raise NotImplementedError, "Method not implemented yet..." + swap(0, @store.length - 1) + removed_node = @store.pop + heap_down(0) + return removed_node.value end @@ -39,7 +44,7 @@ def to_s end output += @store.last.value + "]" - + return output end @@ -47,7 +52,9 @@ def to_s # Time complexity: ? # Space complexity: ? def empty? - raise NotImplementedError, "Method not implemented yet..." + if @store.empty? + return + end end private @@ -58,14 +65,41 @@ def empty? # Time complexity: ? # Space complexity: ? def heap_up(index) - + parent_index = (index - 1) / 2 + + if @store[parent_index].key > @store[index].key && parent_index >= 0 + swap(parent_index, index) + heap_up(parent_index) + else + return + end end - # This helper method takes an index and + # 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..." + left_child = (index * 2) + 1 + right_child = (index * 2) + 2 + + if @store[left_child].nil? + return + end + + if @store[right_child].nil? + if @store[left_child].key < @store[index].key + swap(index, left_child) + end + return + end + + if @store[left_child].key < @store[right_child].key + swap(index, left_child) + heap_down(left_child) + else + swap(index, right_child) + heap_down(right_child) + end end # If you want a swap method... you're welcome From fdcae0a94af4eb2fa35b6f89a84c4eaf0f9f5ea6 Mon Sep 17 00:00:00 2001 From: Faiza Ahsan Date: Sun, 22 Sep 2019 18:15:34 -0700 Subject: [PATCH 2/3] Added code for heapsort --- lib/heap_sort.rb | 18 +++++++++++++++--- lib/min_heap.rb | 11 ++++++----- test/heapsort_test.rb | 12 ++++++------ 3 files changed, 27 insertions(+), 14 deletions(-) diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index c8a32a4..3ba0747 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -1,8 +1,20 @@ - +require_relative './min_heap'; # This method uses a heap to sort an array. # Time Complexity: ? # Space Complexity: ? -def heap_sort(list) - raise NotImplementedError, "Method not implemented yet..." +def heapsort(list) + return list if list.empty? || list.length == 1 + + minHeap = MinHeap.new() + + until list.empty? + minHeap.add(list.pop) + end + + until minHeap.empty? + list << minHeap.remove + end + + return list end \ No newline at end of file diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 04fe4e1..3a47e45 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -67,12 +67,13 @@ def empty? def heap_up(index) parent_index = (index - 1) / 2 - if @store[parent_index].key > @store[index].key && parent_index >= 0 - swap(parent_index, index) - heap_up(parent_index) - else - return + if parent_index >= 0 + if @store[parent_index].key > @store[index].key + swap(parent_index, index) + heap_up(parent_index) + end end + return end # This helper method takes an index and diff --git a/test/heapsort_test.rb b/test/heapsort_test.rb index 34402ac..fb7fa84 100644 --- a/test/heapsort_test.rb +++ b/test/heapsort_test.rb @@ -1,8 +1,8 @@ require_relative "test_helper" -xdescribe "heapsort" do +describe "heapsort" do it "sorts an empty array" do - # Arrange + # Arrange list = [] # Act @@ -13,7 +13,7 @@ end it "can sort a 1-element array" do - # Arrange + # Arrange list = [5] # Act @@ -22,9 +22,9 @@ # Assert expect(result).must_equal [5] end - + it "can sort a 5-element array" do - # Arrange + # Arrange list = [5, 27, 3, 16, -50] # Act @@ -32,5 +32,5 @@ # Assert expect(result).must_equal [-50, 3, 5, 16, 27] - end + end end \ No newline at end of file From 18e657751a2195495ff662d204cb093ef219ec9d Mon Sep 17 00:00:00 2001 From: Faiza Ahsan Date: Thu, 26 Sep 2019 15:09:37 -0700 Subject: [PATCH 3/3] Added Space/Time Complexity --- lib/heap_sort.rb | 4 ++-- lib/min_heap.rb | 16 ++++++++-------- 2 files changed, 10 insertions(+), 10 deletions(-) diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index 3ba0747..e20162a 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -1,8 +1,8 @@ require_relative './min_heap'; # This method uses a heap to sort an array. -# Time Complexity: ? -# Space Complexity: ? +# Time Complexity: O(n), where n is the number of nodes +# Space Complexity: O(1) def heapsort(list) return list if list.empty? || list.length == 1 diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 3a47e45..de89021 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -14,8 +14,8 @@ def initialize end # This method adds a HeapNode instance to the heap - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: O(log n), where n is the number of nodes (at worst there might need to a be a swap at every level) + # Space Complexity: O(1) def add(key, value = key) heap_node = HeapNode.new(key, value) @store.push(heap_node) @@ -24,8 +24,8 @@ def add(key, value = key) # This method removes and returns an element from the heap # maintaining the heap structure - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: O(log n), where n is the number of nodes (at worst there might need to a be a swap at every level) + # Space Complexity: O(1) def remove() swap(0, @store.length - 1) removed_node = @store.pop @@ -49,8 +49,8 @@ def to_s end # This method returns true if the heap is empty - # Time complexity: ? - # Space complexity: ? + # Time complexity: O(n) + # Space complexity: O(1) def empty? if @store.empty? return @@ -62,8 +62,8 @@ 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(n) where n is the number of nodes + # Space complexity: O(1) def heap_up(index) parent_index = (index - 1) / 2