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"use strict";
module.exports = class Queue {
constructor(items) {
this.first = null;
this.last = null;
this.length = 0;
if(items) {
for(const item of items) {
this.enqueue(item);
}
}
}
enqueue(item) {
const first = this.first;
const node = {
item,
next: null
};
if(first === null) {
this.last = node;
} else {
first.next = node;
}
this.first = node;
this.length++;
}
dequeue() {
const last = this.last;
if(last === null)
return undefined;
const next = last.next;
if(next === null) {
this.first = null;
}
this.last = next;
this.length--;
return last.item;
}
};
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