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// Simple doubly linked list (https://en.wikipedia.org/wiki/Doubly_linked_list) implementation
// used for queues. This implementation assumes that the node provided by the user can be modified
// to adjust the next and last properties. We implement only the minimal functionality
// for queue support.
export default class DLL {
constructor() {
this.head = this.tail = null;
this.length = 0;
}
removeLink(node) {
if (node.prev) node.prev.next = node.next;
else this.head = node.next
if (node.next) node.next.prev = node.prev;
else this.tail = node.prev;
node.prev = node.next = null;
this.length -= 1;
return node;
}
empty () {
while(this.head) this.shift();
return this;
}
insertAfter(node, newNode) {
newNode.prev = node;
newNode.next = node.next;
if (node.next) node.next.prev = newNode;
else this.tail = newNode;
node.next = newNode;
this.length += 1;
}
insertBefore(node, newNode) {
newNode.prev = node.prev;
newNode.next = node;
if (node.prev) node.prev.next = newNode;
else this.head = newNode;
node.prev = newNode;
this.length += 1;
}
unshift(node) {
if (this.head) this.insertBefore(this.head, node);
else setInitial(this, node);
}
push(node) {
if (this.tail) this.insertAfter(this.tail, node);
else setInitial(this, node);
}
shift() {
return this.head && this.removeLink(this.head);
}
pop() {
return this.tail && this.removeLink(this.tail);
}
toArray () {
var arr = Array(this.length);
var curr = this.head;
for(var idx = 0; idx < this.length; idx++) {
arr[idx] = curr.data;
curr = curr.next;
}
return arr;
}
remove (testFn) {
var curr = this.head;
while(curr) {
var next = curr.next;
if (testFn(curr)) {
this.removeLink(curr);
}
curr = next;
}
return this;
}
}
function setInitial(dll, node) {
dll.length = 1;
dll.head = dll.tail = node;
}
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