diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index 6b692e4..bfcdafe 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -1,8 +1,21 @@ - +require_relative "./min_heap" # This method uses a heap to sort an array. -# Time Complexity: ? -# Space Complexity: ? +# Time Complexity: O n(log n) +# Space Complexity: O(n) returning_array + internal heap array = O(2n) = O(n)? def heapsort(list) - raise NotImplementedError, "Method not implemented yet..." + heap = MinHeap.new + + #make the minheap tree + list.each do |item| + #add method will sort as adding item to heap + heap.add(item) + end + + returning_list = [] + (list.length).times do |i| + #remove method will pop/return the root aka smallest value + returning_list << heap.remove + end + return returning_list end \ No newline at end of file diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6eaa630..1b38a89 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -8,26 +8,36 @@ def initialize(key, value) end class MinHeap - def initialize @store = [] end # This method adds a HeapNode instance to the heap - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: O(1) + # Space Complexity: O(log n) 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 # maintaining the heap structure - # Time Complexity: ? - # Space Complexity: ? + # Time Complexity: O(1) + # Space Complexity: O(log n) def remove() - raise NotImplementedError, "Method not implemented yet..." - end + if @store.empty? + return nil + end + + #removing the root element + swap(0, @store.length - 1) + result = @store.pop + #re-arranging heap + heap_down(0) unless @store.empty? + return result.value + end # Used for Testing def to_s @@ -39,15 +49,15 @@ def to_s end output += @store.last.value + "]" - + return output 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..." + @store.empty? end private @@ -55,17 +65,42 @@ 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(1) + # Space complexity: O(log n) def heap_up(index) - + parent = (index - 1) / 2 + return if index == 0 + + if @store[parent].key > @store[index].key + swap(parent, index) + heap_up(parent) + else #if @store[parent].key < @store[index].key + 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..." + right = 2 * index + 2 + left = 2 * index + 1 + return if left >= @store.length #return if no child exists + + #initilize smaller in case right index doesn't exist + smaller = left + #determine which is smaller + if @store[right] + smaller = @store[left].key > @store[right].key ? right : left + end + + #swap + if @store[smaller].key < @store[index].key + swap(smaller, index) + heap_down(smaller) + else #if @store[smaller].key > @store[index].key + return + end end # If you want a swap method... you're welcome @@ -74,4 +109,4 @@ def swap(index_1, index_2) @store[index_1] = @store[index_2] @store[index_2] = temp end -end \ No newline at end of file +end 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 = []