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class Node {
constructor(value) {
this.value = value;
this.next = null;
}
}
class LinkedList {
constructor() {
this.head = null;
this.tail = null;
this.length = 0;
}
// Add value to the start of the list
prepend(value) {
const newNode = new Node(value);
if (!this.head) {
this.head = newNode;
this.tail = this.head;
} else {
newNode.next = this.head;
this.head = newNode;
}
this.length++;
}
// Add value to the end of the list
append(value) {
const newNode = new Node(value);
if (!this.head) {
this.head = newNode;
this.tail = this.head;
} else {
this.tail.next = newNode;
this.tail = newNode;
}
this.length++;
}
// Insert value at a specific index in the list
insert(value, index) {
if (index < 0 || index > this.length) {
return false;
}
if (index === 0) {
this.prepend(value);
return true;
}
if (index === this.length) {
this.append(value);
return true;
}
const newNode = new Node(value);
let current = this.head;
let currentIndex = 0;
while (currentIndex !== index - 1) {
current = current.next;
currentIndex++;
}
newNode.next = current.next;
current.next = newNode;
this.length++;
return true;
}
// Remove the value at a specific index from the list
remove(index) {
if (index < 0 || index >= this.length) {
return undefined;
}
if (index === 0) {
const removed = this.head;
this.head = this.head.next;
this.length--;
return removed.value;
}
let current = this.head;
let currentIndex = 0;
while (currentIndex !== index - 1) {
current = current.next;
currentIndex++;
}
const removed = current.next;
current.next = current.next.next;
this.length--;
return removed.value;
}
// Return a string representation of the list
toString() {
let current = this.head;
let result = "";
while (current) {
result += current.value + " -> ";
current = current.next;
}
return result.slice(0, -4);
}
}
const listbox = document.getElementById("listbox");
const textbox = document.getElementById("textbox");
const linkedlistoutput = document.getElementById("linkedlistoutput");
const prependButton = document.getElementById("prepend");
const appendButton = document.getElementById("append");
const insertButton = document.getElementById("insert");
const deleteButton = document.getElementById("delete");
const linkedList = new LinkedList();
// Add initial values from list box to linked list
for (let i = 0; i < listbox.options.length; i++) {
linkedList.append(listbox.options[i].value);
}
linkedlistoutput.value = linkedList.toString();
// Function to update the list box with the current values from the linked list
function updateListbox() {
// Clear the options in the list box
listbox.options.length = 0;
// Add the values from the linked list to the list box
let current = linkedList.head;
while (current) {
listbox.options[listbox.options.length] = new Option(current.value);
current = current.next;
}
}
updateListbox();
listbox.addEventListener("change", function() {
textbox.value = listbox.value;
});
prependButton.addEventListener("click", function() {
linkedList.prepend(textbox.value);
linkedlistoutput.value = linkedList.toString();
updateListbox();
});
appendButton.addEventListener("click", function() {
linkedList.append(textbox.value);
linkedlistoutput.value = linkedList.toString();
updateListbox();
});
insertButton.addEventListener("click", function() {
const selectedIndex = listbox.selectedIndex;
if (selectedIndex === -1) {
alert("you have to select a position in the list box");
} else {
linkedList.insert(textbox.value, selectedIndex);
linkedlistoutput.value = linkedList.toString();
updateListbox();
}
});
deleteButton.addEventListener("click", function() {
const selectedIndex = listbox.selectedIndex;
if (selectedIndex === -1) {
alert("you have to select a position in the list box");
} else {
linkedList.remove(selectedIndex);
linkedlistoutput.value = linkedList.toString();
updateListbox();
}
});
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