Codeforces 1154G（枚举）

Posted 2021-02-16 alphawa

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;
}