From 4ae0c834ce1a6d67fb9e931af61e8b29e2545f8f Mon Sep 17 00:00:00 2001 From: Alice D Date: Sun, 16 May 2021 23:11:58 -0500 Subject: [PATCH 1/8] empty? --- lib/min_heap.rb | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6eaa630..c855597 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -47,7 +47,7 @@ def to_s # Time complexity: ? # Space complexity: ? def empty? - raise NotImplementedError, "Method not implemented yet..." + return true if @store.length == 0 end private From 8a15883db401c003a1d42c94fb4f54b3b1ad7f71 Mon Sep 17 00:00:00 2001 From: Alice D Date: Sun, 16 May 2021 23:15:13 -0500 Subject: [PATCH 2/8] empty? time and space complexity --- lib/min_heap.rb | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index c855597..6bb0050 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -44,8 +44,8 @@ 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 true if @store.length == 0 end From 7485e63b0cb85955274d991361cd09ab5c0c69a6 Mon Sep 17 00:00:00 2001 From: Alice D Date: Mon, 17 May 2021 22:32:37 -0500 Subject: [PATCH 3/8] heap_up --- lib/min_heap.rb | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6bb0050..329da23 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 @@ -55,17 +55,25 @@ 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) + return @store if index == 0 + + parent_index = (1/2)*(index - 1) + return @store if @store[index].key >= @store[parent_index].key + if @store[index].key < @store[parent_index].key + swap(parent_index,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..." end # If you want a swap method... you're welcome From 84276b640d36fc276f210a80d63e42d07ee708ce Mon Sep 17 00:00:00 2001 From: Alice D Date: Mon, 17 May 2021 23:41:57 -0500 Subject: [PATCH 4/8] heap_down --- lib/min_heap.rb | 28 +++++++++++++++++++++++----- 1 file changed, 23 insertions(+), 5 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 329da23..8ce62c5 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -52,8 +52,8 @@ def empty? private - # This helper method takes an index and - # moves it up the heap, if it is less than it's parent node. + # The heap up method takes an index and + # moves it up the heap, if it is less than its parent node. # It could be **very** helpful for the add method. # Time complexity: O(log n) # Space complexity: O(log n) @@ -70,10 +70,28 @@ def heap_up(index) end - # This helper method takes an index and - # moves it up the heap if it's smaller - # than it's parent node. + # The heap down method takes an index and + # moves it DOWN the heap if it's larger + # than its parent node + # Time complexity: O(log n) + # Space complexity: O(log n) + def heap_down(index) + return @store if index == 0 + + left_child_index = 2 * index + 1 + right_child_index = 2 * index + 2 + + if @store[index].key > left_child_index + swap(left_child_index,index) + heap_down(left_child_index) + elsif @store[index].key > right_child_index + swap(left_child_index,index) + heap_down(left_child_index) + else + return @store + end + end # If you want a swap method... you're welcome From 1b080e026be37506cfdc340196bdb05814ec3e95 Mon Sep 17 00:00:00 2001 From: Alice D Date: Mon, 17 May 2021 23:43:02 -0500 Subject: [PATCH 5/8] fixed typo --- lib/min_heap.rb | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 8ce62c5..58c4d20 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -86,8 +86,8 @@ def heap_down(index) swap(left_child_index,index) heap_down(left_child_index) elsif @store[index].key > right_child_index - swap(left_child_index,index) - heap_down(left_child_index) + swap(right_child_index,index) + heap_down(right_child_index) else return @store end From da0efc369641b6f6f38571b8c1a88f5ddd7ff89e Mon Sep 17 00:00:00 2001 From: Alice D Date: Mon, 17 May 2021 23:55:13 -0500 Subject: [PATCH 6/8] add --- lib/min_heap.rb | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 58c4d20..205ca0a 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -14,10 +14,12 @@ def initialize end # This method adds a HeapNode instance to the heap - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: O(log n) + # Space Complexity: O(1) def add(key, value = key) + @store << HeapNode.new(key, value) + heap_up(@store.length - 1) end # This method removes and returns an element from the heap @@ -60,7 +62,7 @@ def empty? def heap_up(index) return @store if index == 0 - parent_index = (1/2)*(index - 1) + parent_index = (index - 1)/2 return @store if @store[index].key >= @store[parent_index].key if @store[index].key < @store[parent_index].key From 19abdaab4067e05e579c3403193e8c9a7128fa45 Mon Sep 17 00:00:00 2001 From: Alice D Date: Tue, 18 May 2021 00:43:55 -0500 Subject: [PATCH 7/8] remove; heap_down fixed --- lib/min_heap.rb | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 205ca0a..5d4c92c 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -24,10 +24,16 @@ 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(1) def remove() - raise NotImplementedError, "Method not implemented yet..." + return nil if @store.empty? + + swap(0, @store.length - 1) + result = @store.pop.value + + heap_down(0) unless @store.empty? + return result end @@ -79,19 +85,19 @@ def heap_up(index) # Space complexity: O(log n) def heap_down(index) - return @store if index == 0 + return @store if index == @store.length - 1 left_child_index = 2 * index + 1 right_child_index = 2 * index + 2 + + if (@store[index].key > @store[left_child_index].key) && (left_child_index < @store.length - 1) + swap(left_child_index, index) + heap_down(index) - if @store[index].key > left_child_index - swap(left_child_index,index) - heap_down(left_child_index) - elsif @store[index].key > right_child_index - swap(right_child_index,index) - heap_down(right_child_index) - else - return @store + end + if (@store[index].key > @store[right_child_index].key) && (right_child_index < @store.length - 1) + swap(right_child_index, index) + heap_down(index) end end From 79869f31227eb2eb943a6d4d37ecbba950c279dc Mon Sep 17 00:00:00 2001 From: Alice D Date: Thu, 20 May 2021 01:38:43 -0500 Subject: [PATCH 8/8] heapsort implemented & heap_down adjusted --- lib/heap_sort.rb | 24 ++++++++++++++++++++---- lib/min_heap.rb | 12 +++++++----- test/heapsort_test.rb | 2 +- 3 files changed, 28 insertions(+), 10 deletions(-) diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index c8a32a4..a3e3c31 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -1,8 +1,24 @@ # This method uses a heap to sort an array. -# Time Complexity: ? -# Space Complexity: ? -def heap_sort(list) - raise NotImplementedError, "Method not implemented yet..." +# Time Complexity: O(n log n) +# Space Complexity: O(n) +def heapsort(list) + heapsorted_array = [] + return heapsorted_array if list.empty? + + heap = MinHeap.new() + + list.each do |item| + heap.add(item) + end + + list.length.times do + removed = heap.remove() + heapsorted_array << removed + end + + return heapsorted_array + + end \ No newline at end of file diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 5d4c92c..2cd8487 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -56,6 +56,7 @@ def to_s # Space complexity: O(1) def empty? return true if @store.length == 0 + return false if @store.length > 0 end private @@ -89,20 +90,21 @@ def heap_down(index) left_child_index = 2 * index + 1 right_child_index = 2 * index + 2 - - if (@store[index].key > @store[left_child_index].key) && (left_child_index < @store.length - 1) + + if (left_child_index < @store.length) && (@store[index].key > @store[left_child_index].key) swap(left_child_index, index) heap_down(index) - end - if (@store[index].key > @store[right_child_index].key) && (right_child_index < @store.length - 1) + + if (right_child_index < @store.length) && (@store[index].key > @store[right_child_index].key) swap(right_child_index, index) heap_down(index) end end - # If you want a swap method... you're welcome + # If you want a swap method... you're welcome; + # thank you :) 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..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 = []