From efcb51beb48082412bdb533333e2239ca962419b Mon Sep 17 00:00:00 2001 From: thenora Date: Mon, 5 Oct 2020 21:31:38 -0700 Subject: [PATCH 1/6] heap_up --- lib/min_heap.rb | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6eaa630..b813449 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -17,7 +17,7 @@ def initialize # Time Complexity: ? # Space Complexity: ? def add(key, value = key) - raise NotImplementedError, "Method not implemented yet..." + end # This method removes and returns an element from the heap @@ -58,7 +58,14 @@ def empty? # Time complexity: ? # Space complexity: ? def heap_up(index) - + parent_index = (index - 1) / 2 + + return if index == 0 + return if @store[index].key > @store[parent_index].key + + swap(index, parent_index) + + heap_up(parent_index) end # This helper method takes an index and From d42542d2af79f5bff334973f1f89603c91100c5b Mon Sep 17 00:00:00 2001 From: thenora Date: Mon, 5 Oct 2020 21:38:21 -0700 Subject: [PATCH 2/6] heap_down --- lib/min_heap.rb | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index b813449..327b162 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -72,7 +72,21 @@ def heap_up(index) # 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_index = index * 2 + 1 + right_index = index * 2 + 2 + + return if left_index >= @store.length + + low_index = left_index + if right_index < @store.length + low_index = @store[left_index].key < @store[child_R].key ? child_L : child_R + end + + return if @store[index].key < @store[low_index].key + + swap(index, low_index) + + heap_down(low_index) end # If you want a swap method... you're welcome From 324defa51db3884b46239cb50cdea4b584b6b102 Mon Sep 17 00:00:00 2001 From: thenora Date: Mon, 5 Oct 2020 21:40:18 -0700 Subject: [PATCH 3/6] add --- lib/min_heap.rb | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 327b162..e56e6fd 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -17,7 +17,10 @@ def initialize # Time Complexity: ? # Space Complexity: ? def add(key, value = key) - + @store << HeapNode.new(key, value) + + last_index = @store.length - 1 + heap_up(last_index) end # This method removes and returns an element from the heap @@ -85,7 +88,7 @@ def heap_down(index) return if @store[index].key < @store[low_index].key swap(index, low_index) - + heap_down(low_index) end From 9f1758406c99e6c3ba4d89a066cccc8b82b38af1 Mon Sep 17 00:00:00 2001 From: thenora Date: Mon, 5 Oct 2020 21:53:11 -0700 Subject: [PATCH 4/6] passing tests --- lib/min_heap.rb | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index e56e6fd..bd34553 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -19,8 +19,7 @@ def initialize def add(key, value = key) @store << HeapNode.new(key, value) - last_index = @store.length - 1 - heap_up(last_index) + heap_up(@store.length - 1) end # This method removes and returns an element from the heap @@ -28,7 +27,12 @@ def add(key, value = key) # Time Complexity: ? # Space Complexity: ? def remove() - raise NotImplementedError, "Method not implemented yet..." + return if @store.empty? + + swap(0, @store.length - 1) + removed = @store.pop + heap_down(0) + return removed.value end @@ -82,7 +86,7 @@ def heap_down(index) low_index = left_index if right_index < @store.length - low_index = @store[left_index].key < @store[child_R].key ? child_L : child_R + low_index = @store[left_index].key < @store[right_index].key ? left_index : right_index end return if @store[index].key < @store[low_index].key From afebe2a3093c5fcac2cd6e346757c4923f952250 Mon Sep 17 00:00:00 2001 From: thenora Date: Mon, 5 Oct 2020 21:57:30 -0700 Subject: [PATCH 5/6] added big O --- lib/min_heap.rb | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index bd34553..dc76766 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) + # Space Complexity: O(log n) def add(key, value = key) @store << HeapNode.new(key, value) @@ -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) + # Space Complexity: O(log n) def remove() return if @store.empty? @@ -51,10 +51,10 @@ 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..." + return @store.empty? end private @@ -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(log n) + # Space complexity: O(log n) def heap_up(index) parent_index = (index - 1) / 2 From af1133f3462910a93b3724e8540161eac1036505 Mon Sep 17 00:00:00 2001 From: thenora Date: Mon, 5 Oct 2020 22:00:33 -0700 Subject: [PATCH 6/6] all tests pass --- lib/heap_sort.rb | 17 ++++++++++++++--- test/heapsort_test.rb | 2 +- 2 files changed, 15 insertions(+), 4 deletions(-) diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index 6b692e4..3c10a8c 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -1,8 +1,19 @@ # This method uses a heap to sort an array. -# Time Complexity: ? -# Space Complexity: ? +# Time Complexity: o(nlog n) +# Space Complexity: O(n) def heapsort(list) - raise NotImplementedError, "Method not implemented yet..." + heap = MinHeap.new + list.each do |n| + heap.add(n) + end + + i = 0 + while i < list.length + list[i] = heap.remove + i += 1 + end + + return list end \ No newline at end of file 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 = []