diff --git a/lib/heap_sort.rb b/lib/heap_sort.rb index c8a32a4..6b692e4 100644 --- a/lib/heap_sort.rb +++ b/lib/heap_sort.rb @@ -3,6 +3,6 @@ # This method uses a heap to sort an array. # Time Complexity: ? # Space Complexity: ? -def heap_sort(list) +def heapsort(list) raise NotImplementedError, "Method not implemented yet..." end \ No newline at end of file diff --git a/lib/min_heap.rb b/lib/min_heap.rb index 6eaa630..ee90986 100644 --- a/lib/min_heap.rb +++ b/lib/min_heap.rb @@ -14,18 +14,33 @@ 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) - raise NotImplementedError, "Method not implemented yet..." + # raise NotImplementedError, "Method not implemented yet..." + heap_node = HeapNode.new(key, value) + @store << heap_node + 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(log n) + # Space Complexity: O(log n) def remove() - raise NotImplementedError, "Method not implemented yet..." + # raise NotImplementedError, "Method not implemented yet..." + if @store.empty? + return nil + end + + swap(0, @store.length - 1) + + removed_node = @store.pop + heap_down(0) unless @store.empty? + + return removed_node.value + end @@ -44,10 +59,11 @@ 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..." + # raise NotImplementedError, "Method not implemented yet..." + return @store.empty? end private @@ -55,17 +71,43 @@ 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_node = (index - 1 ) / 2 + + if @store[parent_node].key > @store[index].key + swap(parent_node, index) + + if parent_node > 0 + return heap_up(parent_node) + end + 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..." + # raise NotImplementedError, "Method not implemented yet..." + left = index * 2 + 1 + right = index * 2 + 2 + min = left + + if left >= @store.length + return + end + + if right < @store.length && @store[right].key < @store[left].key + min = right + end + + if @store[index].key < @store[min].key + return + end + + swap(index, min) + heap_down(min) end # If you want a swap method... you're welcome