前言
本文是博主深感演算法方面的不足，作的一系列讀書筆記和原始碼分析。
原文地址：學習javascript資料結構(二)——連結串列，覺得有用的話可以給個star，謝謝啦。
作者:wengjq
1、連結串列
連結串列儲存有序的元素集合，但不同於陣列，連結串列中的元素在記憶體中並不是連續放置的。每個元素由一個儲存元素本事的節點和一個指向下一個元素的引用組成。相對於傳統的陣列，連結串列的一個好處在於，新增或者刪除元素的時候不需要移動其他元素。然而，連結串列需要使用指標，因此實現連結串列時需要額外注意。
陣列和連結串列的一個不同在於陣列可以直接訪問任何位置的元素，而想要訪問連結串列中的一個元素，需要從起點開始迭代列表。
1.1、單向連結串列
下面是單向連結串列的具體實現程式碼：
function LinkedList() {
var Node = function(element){
this.element = element;
this.next = null;
};
var length = 0;//連結串列長度
var head = null;//第一個節點
this.append = function(element){
var node = new Node(element),
current;
if (head === null){ //列表為空
head = node;
} else { //列表不為空
current = head; //現在只知道第一項head
while(current.next){ //找到列表的最後一項
current = current.next;
}
//建立連結
current.next = node;
}
length++; //更新列表長度
};
this.insert = function(position, element){
//檢查越界值
if (position >= 0 && position <= length){
var node = new Node(element),
current = head,
previous,
index = 0;
if (position === 0){ //在第一個位置新增
node.next = current;
head = node;
} else { //在中間或者尾部新增
while (index++ < position){
previous = current;
current = current.next;
}
node.next = current; //先連上新增的節點
previous.next = node; //再斷開之前的連線
}
length++;
return true;
} else {
return false;
}
};
this.removeAt = function(position){
if (position > -1 && position < length){
var current = head,
previous,
index = 0; //用來迭代列表，直到到達目標位置
if (position === 0){ //移除第一項
head = current.next;
} else { //移除中間或者尾部最後一項
while (index++ < position){
previous = current;
current = current.next;
}
//連線前一項和後一項，跳過當前的項，相當於移除了當前項
previous.next = current.next;
}
length--;
return current.element;
} else {
return null;
}
};
this.remove = function(element){
var index = this.indexOf(element);
return this.removeAt(index);
};
this.indexOf = function(element){
var current = head,
index = 0;
while (current) {
if (element === current.element) {
return index;
}
index++; //記錄位置
current = current.next;
}
return -1;
};
this.isEmpty = function() {
return length === 0;
};
this.size = function() {
return length;
};
this.getHead = function(){
return head;
};
this.toString = function(){
var current = head,
string = '';
while (current) {
string += current.element;//拼接
current = current.next;
}
return string;
};
this.print = function(){
console.log(this.toString());
};
}複製程式碼1.2、雙向連結串列
雙向連結串列和單向連結串列的區別在於，在單向連結串列中，一個節點只有鏈向下一個節點的連結。而在雙向連結串列中，連結是雙向的：一個鏈向下一個元素，另一個鏈向前一個元素。示例程式碼如下：
function DoublyLinkedList() {
var Node = function(element){
this.element = element;
this.next = null;
this.prev = null; //新新增的
};
var length = 0;
var head = null;
var tail = null; //新新增的
this.append = function(element){
var node = new Node(element),
current;
if (head === null){ //列表為空
head = node;
tail = node;
} else {
tail.next = node;
node.prev = tail;
tail = node;
}
length++;
};
this.insert = function(position, element){
if (position >= 0 && position <= length){
var node = new Node(element),
current = head,
previous,
index = 0;
if (position === 0){ //在第一個位置
if (!head){ //列表為空
head = node;
tail = node;
} else { //列表不為空
node.next = current;
current.prev = node;
head = node;
}
} else if (position === length) { //最後一項
current = tail;
current.next = node;
node.prev = current;
tail = node;
} else {
while (index++ < position){
previous = current;
current = current.next;
}
node.next = current;
previous.next = node; //把node節點連線進去前一個節點和後一個節點
current.prev = node; //斷掉之前previous和current的連線
node.prev = previous; //prev同樣需要連線
}
length++;
return true;
} else {
return false;
}
};
this.removeAt = function(position){
if (position > -1 && position < length){
var current = head,
previous,
index = 0;
if (position === 0){ //移除第一項
head = current.next;
if (length === 1){ // 列表只有一項
tail = null;
} else {
head.prev = null;
}
} else if (position === length-1){ 移除最後一項
current = tail; // {4}
tail = current.prev;
tail.next = null;
} else {
while (index++ < position){
previous = current;
current = current.next;
}
previous.next = current.next; // 連結前一項和後一項，跳過當前項
current.next.prev = previous; //修復prev
}
length--;
return current.element;
} else {
return null;
}
};
this.remove = function(element){
var index = this.indexOf(element);
return this.removeAt(index);
};
this.indexOf = function(element){
var current = head,
index = -1;
//檢查第一項
if (element == current.element){
return 0;
}
index++;
//檢查中間項
while(current.next){
if (element == current.element){
return index;
}
current = current.next;
index++;
}
//檢查最後一項
if (element == current.element){
return index;
}
return -1;
};
this.isEmpty = function() {
return length === 0;
};
this. size = function() {
return length;
};
this.toString = function(){
var current = head,
s = current ? current.element : '';
while(current && current.next){
current = current.next;
s += ', ' + current.element;
}
return s;
};
this.inverseToString = function() {
var current = tail,
s = current ? current.element : '';
while(current && current.prev){
current = current.prev;
s += ', ' + current.element;
}
return s;
};
this.print = function(){
console.log(this.toString());
};
this.printInverse = function(){
console.log(this.inverseToString());
};
this.getHead = function(){
return head;
};
this.getTail = function(){
return tail;
}
}複製程式碼1.3、迴圈連結串列
迴圈連結串列可以像單向連結串列那樣只有單向引用，也可以像雙向連結串列那樣有雙向引用。迴圈連結串列和其他連結串列的區別在於最後一個元素指向下一個元素的引用不是null，而是指向第一個元素（head）。示例程式碼如下：
function CircularLinkedList() {
var Node = function(element){
this.element = element;
this.next = null;
};
var length = 0;
var head = null;
this.append = function(element){
var node = new Node(element),
current;
if (head === null){ //列表為空
head = node;
} else {
current = head;
while(current.next !== head){ //最後一個元素將是head，而不是null
current = current.next;
}
current.next = node; //建立連線
}
node.next = head; //首尾相連起來變成一個環列表
length++;
};
this.insert = function(position, element){
if (position >= 0 && position <= length){
var node = new Node(element),
current = head,
previous,
index = 0;
if (position === 0){ //在第一項
node.next = current;
while(current.next !== head){
current = current.next;
}
head = node;
current.next = head;
} else {
while (index++ < position){
previous = current;
current = current.next;
}
node.next = current;
previous.next = node;
if (node.next === null){ //在最後一個元素更新
node.next = head;
}
}
length++;
return true;
} else {
return false;
}
};
this.removeAt = function(position){
if (position > -1 && position < length){
var current = head,
previous,
index = 0;
if (position === 0){
while(current.next !== head){
current = current.next;
}
head = head.next;
current.next = head; //更新最後一項
} else {
while (index++ < position){
previous = current;
current = current.next;
}
previous.next = current.next;
}
length--;
return current.element;
} else {
return null;
}
};
this.remove = function(element){
var index = this.indexOf(element);
return this.removeAt(index);
};
this.indexOf = function(element){
var current = head,
index = -1;
if (element == current.element){ //檢查第一項
return 0;
}
index++;
while(current.next !== head){ //檢查列表中間
if (element == current.element){
return index;
}
current = current.next;
index++;
}
if (element == current.element){ //檢查最後一項
return index;
}
return -1;
};
this.isEmpty = function() {
return length === 0;
};
this.size = function() {
return length;
};
this.getHead = function(){
return head;
};
this.toString = function(){
var current = head,
s = current.element;
while(current.next !== head){
current = current.next;
s += ', ' + current.element;
}
return s.toString();
};
this.print = function(){
console.log(this.toString());
};
}複製程式碼