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168 changes: 104 additions & 64 deletions data-structures-in-javascript/doubly-linked-list.es6.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6,102 +6,141 @@ function Node(data) {

class DoublyLinkedList {
constructor() {
this.head = null;
this.tail = null;
const dummyNode = new Node(undefined);
dummyNode.next = dummyNode;
dummyNode.previous = dummyNode;
this.dummy = dummyNode;
this.numberOfValues = 0;
}

add(data) {
const node = new Node(data);
if(!this.head) {
this.head = node;
this.tail = node;
} else {
node.previous = this.tail;
this.tail.next = node;
this.tail = node;
/* this should be a private method */
getNode(i){
let node = undefined;
if(i < Math.floor(this.numberOfValues/2)){
node = this.dummy.next;
for(let j = 0; j < i; j++){
node = node.next;
}
} else{
node = this.dummy;
for(let j = this.numberOfValues; j > i; j--){
node = node.previous;
}
}
return node;
}

/* gets a values within the range of 0 > i >= n */
get(i){
if(0 > i || i >= this.numberOfValues) return undefined;
return this.getNode(i).data;
}

/* sets a value withing the range 0 > i >= n */
set(i,x){
if(0 > i || i >= this.numberOfValues) return undefined;
let node = getNode(i);
let temp = node.data;
node.data = x;
return temp;
}

/* this should be a private method*/
addBefore(node,x) {
const toAdd = new Node(x);

toAdd.previous = node.previous;
toAdd.next = node;


toAdd.next.previous = toAdd;
toAdd.previous.next = toAdd;

this.numberOfValues++;

return toAdd;
}

remove(data) {
let current = this.head;
while(current) {
if(current.data === data) {
if(current === this.head && current === this.tail) {
this.head = null;
this.tail = null;
} else if(current === this.head) {
this.head = this.head.next;
this.head.previous = null;
} else if(current === this.tail) {
this.tail = this.tail.previous;
this.tail.next = null;
} else {
current.previous.next = current.next;
current.next.previous = current.previous;
}
this.numberOfValues--;
}
current = current.next;
}
/* adds a node at i within the range of 0 > i > n */
add(i,x){
if(0 > i || i > this.numberOfValues) return;
this.addBefore(this.getNode(i),x);
}

insertAfter(data, toNodeData) {
let current = this.head;
while(current) {
if(current.data === toNodeData) {
const node = new Node(data);
if(current === this.tail) {
this.add(data);
} else {
current.next.previous = node;
node.previous = current;
node.next = current.next;
current.next = node;
this.numberOfValues++;
}
}
current = current.next;
}
/* this should be a private method */
removeNode(x){
x.previous.next = x.next;
x.next.previous = x.previous;
this.numberOfValues--;
}

traverse(fn) {
let current = this.head;
while(current) {
if(fn) {
fn(current);
}
current = current.next;
}
/* remeoves a node within the range of 0 > i >= n */
remove(i){
if(0 > i || i >= this.numberOfValues) return undefined;
let node = this.getNode(i);
this.removeNode(node);
return node.data;
}

traverseReverse(fn) {
let current = this.tail;
while(current) {
/* apply a function to the entire data set */
map(fn) {
let current = this.dummy.next;
for(let i = 0; i < this.numberOfValues; i++){
if(fn) {
fn(current);
current.data = fn(current.data);
}
current = current.previous;
current = current.next;
}
}

/* returns the size of the list */
length() {
return this.numberOfValues;
}

/* prints out the list */
print() {
let string = '';
let current = this.head;
while(current) {
let current = this.dummy.next;
for(let i = 0; i < this.numberOfValues; i++){
string += `${current.data} `;
current = current.next;
}
console.log(string.trim());
}
}

/* tester data */

const doublyLinkedList = new DoublyLinkedList();

doublyLinkedList.print(); // => ''
for(let i = 0; i < 10; i++){
doublyLinkedList.add(doublyLinkedList.length(),i);
}
doublyLinkedList.map(function(val){return 10*val;});
doublyLinkedList.print(); //=> 0 10 20 30 40 50 60 70 80 90

for(let i = 0; i < doublyLinkedList.length();i++){
console.log(doublyLinkedList.get(i)); //=> 0\n10\n20\n30\n40\n50\n60\n70\n80\n90\n
}
doublyLinkedList.remove(0);
doublyLinkedList.remove(doublyLinkedList.length()-1);
doublyLinkedList.print(); // => 10 20 30 40 50 60 70 80
console.log(doublyLinkedList.length()); // => 8

/* these line should all print out undefined */
console.log(doublyLinkedList.get(-1));
console.log(doublyLinkedList.get(doublyLinkedList.length()));
console.log(doublyLinkedList.set(-1,10));
console.log(doublyLinkedList.set(doublyLinkedList.length(),10));
console.log(doublyLinkedList.add(-1,10));
console.log(doublyLinkedList.add(doublyLinkedList.length() + 1,10));
doublyLinkedList.print(); // => 10 20 30 40 50 60 70 80
doublyLinkedList.add(0,-10);
doublyLinkedList.print(); // => -10 10 20 30 40 50 60 70 80

/*
doublyLinkedList.print(); // => ''
doublyLinkedList.add(1);
doublyLinkedList.add(2);
Expand Down Expand Up @@ -144,3 +183,4 @@ console.log('length is 7:', doublyLinkedList.length()); // => 7
doublyLinkedList.traverseReverse(node => { console.log(node.data); }); // => 18 17 16 15 14 13 12
doublyLinkedList.print(); // => 12 13 14 15 16 17 18
console.log('length is 7:', doublyLinkedList.length()); // => 7
*/