mirror of
https://github.com/Luzifer/ansible-role-version.git
synced 2024-12-24 11:31:21 +00:00
164 lines
4.9 KiB
Go
164 lines
4.9 KiB
Go
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// Copyright (c) 2015, Emir Pasic. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package binaryheap implements a binary heap backed by array list.
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//
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// Comparator defines this heap as either min or max heap.
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//
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// Structure is not thread safe.
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//
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// References: http://en.wikipedia.org/wiki/Binary_heap
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package binaryheap
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import (
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"fmt"
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"github.com/emirpasic/gods/lists/arraylist"
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"github.com/emirpasic/gods/trees"
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"github.com/emirpasic/gods/utils"
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"strings"
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)
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func assertTreeImplementation() {
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var _ trees.Tree = (*Heap)(nil)
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}
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// Heap holds elements in an array-list
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type Heap struct {
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list *arraylist.List
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Comparator utils.Comparator
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}
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// NewWith instantiates a new empty heap tree with the custom comparator.
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func NewWith(comparator utils.Comparator) *Heap {
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return &Heap{list: arraylist.New(), Comparator: comparator}
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}
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// NewWithIntComparator instantiates a new empty heap with the IntComparator, i.e. elements are of type int.
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func NewWithIntComparator() *Heap {
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return &Heap{list: arraylist.New(), Comparator: utils.IntComparator}
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}
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// NewWithStringComparator instantiates a new empty heap with the StringComparator, i.e. elements are of type string.
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func NewWithStringComparator() *Heap {
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return &Heap{list: arraylist.New(), Comparator: utils.StringComparator}
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}
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// Push adds a value onto the heap and bubbles it up accordingly.
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func (heap *Heap) Push(values ...interface{}) {
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if len(values) == 1 {
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heap.list.Add(values[0])
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heap.bubbleUp()
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} else {
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// Reference: https://en.wikipedia.org/wiki/Binary_heap#Building_a_heap
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for _, value := range values {
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heap.list.Add(value)
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}
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size := heap.list.Size()/2 + 1
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for i := size; i >= 0; i-- {
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heap.bubbleDownIndex(i)
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}
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}
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}
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// Pop removes top element on heap and returns it, or nil if heap is empty.
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// Second return parameter is true, unless the heap was empty and there was nothing to pop.
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func (heap *Heap) Pop() (value interface{}, ok bool) {
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value, ok = heap.list.Get(0)
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if !ok {
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return
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}
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lastIndex := heap.list.Size() - 1
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heap.list.Swap(0, lastIndex)
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heap.list.Remove(lastIndex)
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heap.bubbleDown()
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return
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}
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// Peek returns top element on the heap without removing it, or nil if heap is empty.
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// Second return parameter is true, unless the heap was empty and there was nothing to peek.
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func (heap *Heap) Peek() (value interface{}, ok bool) {
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return heap.list.Get(0)
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}
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// Empty returns true if heap does not contain any elements.
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func (heap *Heap) Empty() bool {
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return heap.list.Empty()
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}
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// Size returns number of elements within the heap.
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func (heap *Heap) Size() int {
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return heap.list.Size()
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}
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// Clear removes all elements from the heap.
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func (heap *Heap) Clear() {
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heap.list.Clear()
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}
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// Values returns all elements in the heap.
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func (heap *Heap) Values() []interface{} {
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return heap.list.Values()
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}
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// String returns a string representation of container
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func (heap *Heap) String() string {
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str := "BinaryHeap\n"
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values := []string{}
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for _, value := range heap.list.Values() {
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values = append(values, fmt.Sprintf("%v", value))
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}
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str += strings.Join(values, ", ")
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return str
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}
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// Performs the "bubble down" operation. This is to place the element that is at the root
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// of the heap in its correct place so that the heap maintains the min/max-heap order property.
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func (heap *Heap) bubbleDown() {
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heap.bubbleDownIndex(0)
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}
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// Performs the "bubble down" operation. This is to place the element that is at the index
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// of the heap in its correct place so that the heap maintains the min/max-heap order property.
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func (heap *Heap) bubbleDownIndex(index int) {
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size := heap.list.Size()
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for leftIndex := index<<1 + 1; leftIndex < size; leftIndex = index<<1 + 1 {
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rightIndex := index<<1 + 2
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smallerIndex := leftIndex
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leftValue, _ := heap.list.Get(leftIndex)
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rightValue, _ := heap.list.Get(rightIndex)
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if rightIndex < size && heap.Comparator(leftValue, rightValue) > 0 {
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smallerIndex = rightIndex
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}
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indexValue, _ := heap.list.Get(index)
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smallerValue, _ := heap.list.Get(smallerIndex)
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if heap.Comparator(indexValue, smallerValue) > 0 {
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heap.list.Swap(index, smallerIndex)
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} else {
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break
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}
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index = smallerIndex
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}
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}
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// Performs the "bubble up" operation. This is to place a newly inserted
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// element (i.e. last element in the list) in its correct place so that
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// the heap maintains the min/max-heap order property.
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func (heap *Heap) bubbleUp() {
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index := heap.list.Size() - 1
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for parentIndex := (index - 1) >> 1; index > 0; parentIndex = (index - 1) >> 1 {
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indexValue, _ := heap.list.Get(index)
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parentValue, _ := heap.list.Get(parentIndex)
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if heap.Comparator(parentValue, indexValue) <= 0 {
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break
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}
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heap.list.Swap(index, parentIndex)
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index = parentIndex
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}
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}
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// Check that the index is within bounds of the list
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func (heap *Heap) withinRange(index int) bool {
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return index >= 0 && index < heap.list.Size()
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}
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