選択できるのは25トピックまでです。
トピックは、先頭が英数字で、英数字とダッシュ('-')を使用した35文字以内のものにしてください。
63 行
1.5 KiB
63 行
1.5 KiB
export class MRU<T> {
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private stack: T[] = [];
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constructor(public readonly maxSize: number = 10, private readonly comparator?: (a: T, b: T) => boolean) {}
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get count(): number {
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return this.stack.length;
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}
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private _position: number = 0;
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get position(): number {
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return this._position;
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}
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add(item: T): void {
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if (this._position > 0) {
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this.stack.splice(0, this._position);
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this._position = 0;
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}
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const index =
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this.comparator != null ? this.stack.findIndex(i => this.comparator!(item, i)) : this.stack.indexOf(item);
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if (index !== -1) {
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this.stack.splice(index, 1);
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} else if (this.stack.length === this.maxSize) {
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this.stack.pop();
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}
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this.stack.unshift(item);
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this._position = 0;
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}
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get(position?: number): T | undefined {
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if (position != null) {
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if (position < 0 || position >= this.stack.length) return undefined;
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return this.stack[position];
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}
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return this.stack.length > 0 ? this.stack[0] : undefined;
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}
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insert(item: T): void {
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if (this._position > 0) {
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this.stack.splice(0, this._position);
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this._position = 0;
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}
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this.stack.unshift(item);
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this._position++;
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}
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navigate(direction: 'back' | 'forward'): T | undefined {
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if (this.stack.length <= 1) return undefined;
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if (direction === 'back') {
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if (this._position >= this.stack.length - 1) return undefined;
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this._position += 1;
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} else {
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if (this._position <= 0) return undefined;
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this._position -= 1;
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}
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return this.stack[this._position];
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}
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}
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