src/vs/base/browser/ui/list/listWidget.ts/relativeComplement
function relativeComplement(one: number[], other: number[]): number[] {
	const result: number[] = [];
	let i = 0, j = 0;

	while (i < one.length || j < other.length) {
		if (i >= one.length) {
			result.push(other[j++]);
		} else if (j >= other.length) {
			result.push(one[i++]);
		} else if (one[i] === other[j]) {
			i++;
			j++;
			continue;
		} else if (one[i] < other[j]) {
			result.push(one[i++]);
		} else {
			j++;
		}
	}

	return result;
}