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