golang list 代码
文件路径：/src/container/list/list.go
/ Copyright 2009 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
/ Package list implements a doubly linked list.
/
/ To iterate over a list (where l is a *List):
/
/ for e := l.Front(); e != nil; e = e.Next() {
/ / do something with e.Value
/ }
package list
/ Element is an element of a linked list.
type Element struct {
/ Next and previous pointers in the doubly-linked list of elements.
/ To simplify the implementation, internally a list l is implemented
/ as a ring, such that &l.root is both the next element of the last
/ list element (l.Back()) and the previous element of the first list
/ element (l.Front()).
next, prev *Element
/ The list to which this element belongs.
list *List
/ The value stored with this element.
Value any
}
/ Next returns the next list element or nil.
func (e *Element) Next() *Element {
if p := e.next; e.list != nil && p != &e.list.root {
return p
}
return nil
}
/ Prev returns the previous list element or nil.
func (e *Element) Prev() *Element {
if p := e.prev; e.list != nil && p != &e.list.root {
return p
}
return nil
}
/ List represents a doubly linked list.
/ The zero value for List is an empty list ready to use.
type List struct {
root Element / sentinel list element, only &root, root.prev, and root.next are used
len int / current list length excluding (this) sentinel element
}
/ Init initializes or clears list l.
func (l *List) Init() *List {
l.root.next = &l.root
l.root.prev = &l.root
l.len = 0
return l
}
/ New returns an initialized list.
func New() *List { return new(List).Init() }
/ Len returns the number of elements of list l.
/ The complexity is O(1).
func (l *List) Len() int { return l.len }
/ Front returns the first element of list l or nil if the list is empty.
func (l *List) Front() *Element {
if l.len == 0 {
return nil
}
return l.root.next
}
/ Back returns the last element of list l or nil if the list is empty.
func (l *List) Back() *Element {
if l.len == 0 {
return nil
}
return l.root.prev
}
/ lazyInit lazily initializes a zero List value.
func (l *List) lazyInit() {
if l.root.next == nil {
l.Init()
}
}
/ insert inserts e after at, increments l.len, and returns e.
func (l *List) insert(e, at *Element) *Element {
e.prev = at
e.next = at.next
e.prev.next = e
e.next.prev = e
e.list = l
l.len++
return e
}
/ insertValue is a convenience wrapper for insert(&Element{Value: v}, at).
func (l *List) insertValue(v any, at *Element) *Element {
return l.insert(&Element{Value: v}, at)
}
/ remove removes e from its list, decrements l.len
func (l *List) remove(e *Element) {
e.prev.next = e.next
e.next.prev = e.prev
e.next = nil / avoid memory leaks
e.prev = nil / avoid memory leaks
e.list = nil
l.len--
}
/ move moves e to next to at.
func (l *List) move(e, at *Element) {
if e == at {
return
}
e.prev.next = e.next
e.next.prev = e.prev
e.prev = at
e.next = at.next
e.prev.next = e
e.next.prev = e
}
/ Remove removes e from l if e is an element of list l.
/ It returns the element value e.Value.
/ The element must not be nil.
func (l *List) Remove(e *Element) any {
if e.list == l {
/ if e.list == l, l must have been initialized when e was inserted
/ in l or l == nil (e is a zero Element) and l.remove will crash
l.remove(e)
}
return e.Value
}
/ PushFront inserts a new element e with value v at the front of list l and returns e.
func (l *List) PushFront(v any) *Element {
l.lazyInit()
return l.insertValue(v, &l.root)
}
/ PushBack inserts a new element e with value v at the back of list l and returns e.
func (l *List) PushBack(v any) *Element {
l.lazyInit()
return l.insertValue(v, l.root.prev)
}
/ InsertBefore inserts a new element e with value v immediately before mark and returns e.
/ If mark is not an element of l, the list is not modified.
/ The mark must not be nil.
func (l *List) InsertBefore(v any, mark *Element) *Element {
if mark.list != l {
return nil
}
/ see comment in List.Remove about initialization of l
return l.insertValue(v, mark.prev)
}
/ InsertAfter inserts a new element e with value v immediately after mark and returns e.
/ If mark is not an element of l, the list is not modified.
/ The mark must not be nil.
func (l *List) InsertAfter(v any, mark *Element) *Element {
if mark.list != l {
return nil
}
/ see comment in List.Remove about initialization of l
return l.insertValue(v, mark)
}
/ MoveToFront moves element e to the front of list l.
/ If e is not an element of l, the list is not modified.
/ The element must not be nil.
func (l *List) MoveToFront(e *Element) {
if e.list != l || l.root.next == e {
return
}
/ see comment in List.Remove about initialization of l
l.move(e, &l.root)
}
/ MoveToBack moves element e to the back of list l.
/ If e is not an element of l, the list is not modified.
/ The element must not be nil.
func (l *List) MoveToBack(e *Element) {
if e.list != l || l.root.prev == e {
return
}
/ see comment in List.Remove about initialization of l
l.move(e, l.root.prev)
}
/ MoveBefore moves element e to its new position before mark.
/ If e or mark is not an element of l, or e == mark, the list is not modified.
/ The element and mark must not be nil.
func (l *List) MoveBefore(e, mark *Element) {
if e.list != l || e == mark || mark.list != l {
return
}
l.move(e, mark.prev)
}
/ MoveAfter moves element e to its new position after mark.
/ If e or mark is not an element of l, or e == mark, the list is not modified.
/ The element and mark must not be nil.
func (l *List) MoveAfter(e, mark *Element) {
if e.list != l || e == mark || mark.list != l {
return
}
l.move(e, mark)
}
/ PushBackList inserts a copy of another list at the back of list l.
/ The lists l and other may be the same. They must not be nil.
func (l *List) PushBackList(other *List) {
l.lazyInit()
for i, e := other.Len(), other.Front(); i > 0; i, e = i-1, e.Next() {
l.insertValue(e.Value, l.root.prev)
}
}
/ PushFrontList inserts a copy of another list at the front of list l.
/ The lists l and other may be the same. They must not be nil.
func (l *List) PushFrontList(other *List) {
l.lazyInit()
for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() {
l.insertValue(e.Value, &l.root)
}
}