10分的疑惑

for (int i = 1; i <= n; i++) {
		cin >> a[i];
		ls1[i] = a[i];
	}
	for (int i = 1; i <= n; i++) {
		cin >> b[i];
		ls2[i] = b[i];
	}
	sort(a + 1, a + 1 + n);
	sort(b + 1, b + 1 + n);
	for (int i = 1; i <= n; i++) {
		ls1[i] = lower_bound(a + 1, a + n + 1, ls1[i]) - a;
	}
	for (int i = 1; i <= n; i++) {
		ls2[i] = lower_bound(b + 1, b + n + 1, ls2[i]) - b;
	}
	for (int i = 1; i <= n; i++) {
		q[ls1[i]] = ls2[i];
	}