Codeforces 1154G（枚举）

我预处理(1e7log(1e7))的因数被T掉了，就不敢往这个复杂度想了……无奈去看AC代码
结果怎么暴举gcd剪一剪小枝就接近3s卡过去了！vector有锅（确信

const int maxn = 1e6 + 5, maxa = 1e7 + 5;
int n, a, l, r;
ll lcm = INF;
int f[maxa], s[maxa];

int main() {
	read(n);
	rep(i, 1, n) {
		read(a);
		if (f[a])	s[a] = i;
		else	f[a] = i;
	}
	rep(d, 1, maxa - 5) {
		vector<pii> v;
		for (int j = 1; j * d <= maxa - 5; j++) {
			if (v.size() >= 2)	break;
			if (f[j * d])	v.push_back({j * d, f[j * d]});
			if (s[j * d])	v.push_back({j * d, s[j * d]});
		}
		if (v.size() < 2)	continue;
		ll tmp = (ll)v[0].first / d * v[1].first;
		if (lcm > tmp) {
			lcm = tmp;
			l = v[0].second;
			r = v[1].second;
		}
	}
	if (l > r)	swap(l, r);
	printf("%d %d
", l, r);
	return 0;
}