12345678910111213141516
export default function singleNumber(nums: number[]): number[] {    const set = new Set<number>();    nums.forEach((item) => {        if (set.has(item)) {            set.delete(item);        } else {            set.add(item);        }    });    const arr: number[] = [];    set.forEach((item) => {        arr.push(item);    });    return arr;}