aaac7fed
 liuqimichale
add
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function Queue() {
this.head = new Item('head', null);
}
module.exports = Queue;
Queue.prototype.append = function append(kind, value) {
var item = new Item(kind, value);
this.head.prepend(item);
return item;
};
Queue.prototype.isEmpty = function isEmpty() {
return this.head.prev === this.head;
};
Queue.prototype.first = function first() {
return this.head.next;
};
function Item(kind, value) {
this.prev = this;
this.next = this;
this.kind = kind;
this.value = value;
}
Item.prototype.prepend = function prepend(other) {
other.prev = this.prev;
other.next = this;
other.prev.next = other;
other.next.prev = other;
};
Item.prototype.dequeue = function dequeue() {
var prev = this.prev;
var next = this.next;
prev.next = next;
next.prev = prev;
this.prev = this;
this.next = this;
return this.value;
};
Item.prototype.isEmpty = function isEmpty() {
return this.prev === this;
};
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