forked from emirpasic/gods
/
doublylinkedlist.go
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/
doublylinkedlist.go
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// Copyright (c) 2015, Emir Pasic. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package doublylinkedlist implements the doubly-linked list.
//
// Structure is not thread safe.
//
// Reference: https://en.wikipedia.org/wiki/List_%28abstract_data_type%29
package doublylinkedlist
import (
"fmt"
"github.com/emirpasic/gods/lists"
"github.com/emirpasic/gods/utils"
"strings"
)
func assertListImplementation() {
var _ lists.List = (*List)(nil)
}
// List holds the elements, where each element points to the next and previous element
type List struct {
first *element
last *element
size int
}
type element struct {
value interface{}
prev *element
next *element
}
// New instantiates a new empty list
func New() *List {
return &List{}
}
// Add appends a value (one or more) at the end of the list (same as Append())
func (list *List) Add(values ...interface{}) {
for _, value := range values {
newElement := &element{value: value, prev: list.last}
if list.size == 0 {
list.first = newElement
list.last = newElement
} else {
list.last.next = newElement
list.last = newElement
}
list.size++
}
}
// Append appends a value (one or more) at the end of the list (same as Add())
func (list *List) Append(values ...interface{}) {
list.Add(values...)
}
// Prepend prepends a values (or more)
func (list *List) Prepend(values ...interface{}) {
// in reverse to keep passed order i.e. ["c","d"] -> Prepend(["a","b"]) -> ["a","b","c",d"]
for v := len(values) - 1; v >= 0; v-- {
newElement := &element{value: values[v], next: list.first}
if list.size == 0 {
list.first = newElement
list.last = newElement
} else {
list.first.prev = newElement
list.first = newElement
}
list.size++
}
}
// Get returns the element at index.
// Second return parameter is true if index is within bounds of the array and array is not empty, otherwise false.
func (list *List) Get(index int) (interface{}, bool) {
if !list.withinRange(index) {
return nil, false
}
// determine traveral direction, last to first or first to last
if list.size-index < index {
element := list.last
for e := list.size - 1; e != index; e, element = e-1, element.prev {
}
return element.value, true
}
element := list.first
for e := 0; e != index; e, element = e+1, element.next {
}
return element.value, true
}
// Remove removes one or more elements from the list with the supplied indices.
func (list *List) Remove(index int) {
if !list.withinRange(index) {
return
}
if list.size == 1 {
list.Clear()
return
}
var element *element
// determine traversal direction, last to first or first to last
if list.size-index < index {
element = list.last
for e := list.size - 1; e != index; e, element = e-1, element.prev {
}
} else {
element = list.first
for e := 0; e != index; e, element = e+1, element.next {
}
}
if element == list.first {
list.first = element.next
}
if element == list.last {
list.last = element.prev
}
if element.prev != nil {
element.prev.next = element.next
}
if element.next != nil {
element.next.prev = element.prev
}
element = nil
list.size--
}
// Contains check if values (one or more) are present in the set.
// All values have to be present in the set for the method to return true.
// Performance time complexity of n^2.
// Returns true if no arguments are passed at all, i.e. set is always super-set of empty set.
func (list *List) Contains(values ...interface{}) bool {
if len(values) == 0 {
return true
}
if list.size == 0 {
return false
}
for _, value := range values {
found := false
for element := list.first; element != nil; element = element.next {
if element.value == value {
found = true
break
}
}
if !found {
return false
}
}
return true
}
// Values returns all elements in the list.
func (list *List) Values() []interface{} {
values := make([]interface{}, list.size, list.size)
for e, element := 0, list.first; element != nil; e, element = e+1, element.next {
values[e] = element.value
}
return values
}
// Empty returns true if list does not contain any elements.
func (list *List) Empty() bool {
return list.size == 0
}
// Size returns number of elements within the list.
func (list *List) Size() int {
return list.size
}
// Clear removes all elements from the list.
func (list *List) Clear() {
list.size = 0
list.first = nil
list.last = nil
}
// Sort sorts values (in-place) using.
func (list *List) Sort(comparator utils.Comparator) {
if list.size < 2 {
return
}
values := list.Values()
utils.Sort(values, comparator)
list.Clear()
list.Add(values...)
}
// Swap swaps values of two elements at the given indices.
func (list *List) Swap(i, j int) {
if list.withinRange(i) && list.withinRange(j) && i != j {
var element1, element2 *element
for e, currentElement := 0, list.first; element1 == nil || element2 == nil; e, currentElement = e+1, currentElement.next {
switch e {
case i:
element1 = currentElement
case j:
element2 = currentElement
}
}
element1.value, element2.value = element2.value, element1.value
}
}
// Insert inserts values at specified index position shifting the value at that position (if any) and any subsequent elements to the right.
// Does not do anything if position is negative or bigger than list's size
// Note: position equal to list's size is valid, i.e. append.
func (list *List) Insert(index int, values ...interface{}) {
if !list.withinRange(index) {
// Append
if index == list.size {
list.Add(values...)
}
return
}
list.size += len(values)
var beforeElement *element
var foundElement *element
// determine traversal direction, last to first or first to last
if list.size-index < index {
foundElement = list.last
for e := list.size - 1; e != index; e, foundElement = e-1, foundElement.prev {
beforeElement = foundElement.prev
}
} else {
foundElement = list.first
for e := 0; e != index; e, foundElement = e+1, foundElement.next {
beforeElement = foundElement
}
}
if foundElement == list.first {
oldNextElement := list.first
for i, value := range values {
newElement := &element{value: value}
if i == 0 {
list.first = newElement
} else {
beforeElement.next = newElement
}
beforeElement = newElement
}
beforeElement.next = oldNextElement
} else {
oldNextElement := beforeElement.next
for _, value := range values {
newElement := &element{value: value}
beforeElement.next = newElement
beforeElement = newElement
}
beforeElement.next = oldNextElement
}
}
// String returns a string representation of container
func (list *List) String() string {
str := "DoublyLinkedList\n"
values := []string{}
for element := list.first; element != nil; element = element.next {
values = append(values, fmt.Sprintf("%v", element.value))
}
str += strings.Join(values, ", ")
return str
}
// Check that the index is within bounds of the list
func (list *List) withinRange(index int) bool {
return index >= 0 && index < list.size
}