Submission #464937

#	Time	Username	Problem	Language	Result	Execution time	Memory
464937		SamAnd	Exam (eJOI20_exam)	C++17	78 / 100	1098 ms	175660 KiB

exam

#include <bits/stdc++.h>
using namespace std;
#define m_p make_pair
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define fi first
#define se second
typedef long long ll;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
mt19937 rnf(2106);
const int N = 100005, N0 = 5003;
int M = 25000007;

bool isprime(int x)
{
    if (x <= 1)
        return false;
    for (int i = 2; i * i <= x; ++i)
    {
        if (x % i == 0)
            return false;
    }
    return true;
}

int n;
int a[N], b[N];

int ul[N], ur[N];
void pre()
{
    stack<int> s;
    for (int i = 1; i <= n; ++i)
    {
        while (!s.empty() && a[s.top()] <= a[i])
            s.pop();
        if (s.empty())
            ul[i] = 0;
        else
            ul[i] = s.top();
        s.push(i);
    }
    while (!s.empty())
        s.pop();
    for (int i = n; i >= 1; --i)
    {
        while (!s.empty() && a[s.top()] <= a[i])
            s.pop();
        if (s.empty())
            ur[i] = n + 1;
        else
            ur[i] = s.top();
        s.push(i);
    }
}

int maxi[N0][N0];

vector<int> v[N];

void rec0(int l, int r, int p)
{
    if (l > r)
        return;
    int m = maxi[l][r];
    rec0(l, m - 1, m);
    rec0(m + 1, r, m);

    if (p == 0)
        return;
    else if (p == l - 1)
    {
        for (int i = l; i <= r; ++i)
        {
            if (b[i] == a[p])
                v[m].push_back(i);
        }
    }
    else if (p == r + 1)
    {
        for (int i = r; i >= l; --i)
        {
            if (b[i] == a[p])
                v[m].push_back(i);
        }
        reverse(all(v[m]));
    }
    else
        assert(false);
}

int* dp;
int rec(int l, int r, int ul, int ur, int p)
{
    if (l > r)
        return 0;
    ul = max(ul, l - 1);
    ur = min(ur, r + 1);
    if (ul + 1 >= ur)
        return 0;

    int m = maxi[l][r];

    ll h = (ul * 1LL * N0 * N0 + m * 1LL * N0 + ur) % M;

    if (dp[h] != -1)
        return dp[h];

    if (ul < m && m < ur && a[m] == b[m])
        dp[h] = rec(l, m - 1, ul, ur, m) + rec(m + 1, r, ul, ur, m) + 1;
    else
        dp[h] = rec(l, m - 1, ul, ur, m) + rec(m + 1, r, ul, ur, m);

    if (p == 0)
    {
        return dp[h];
    }

    if (p == l - 1)
    {
        int q = 0;
        //for (int i = ul + 1; i <= ur - 1; ++i)
        int s = upper_bound(all(v[m]), ul) - v[m].begin();
        for (int ii = s; ii < sz(v[m]); ++ii)
        {
            int i = v[m][ii];

            if (!(ul < i && i < ur))
                break;

            bool z = false;
            if (b[i] == a[p])
            {
                z = true;
                ++q;
            }
            if (i < m && m < ur && a[m] == b[m])
                ++q;
            if (z)
                dp[h] = max(dp[h], q + rec(l, m - 1, i, ur, m) + rec(m + 1, r, i, ur, m));
            if (i < m && m < ur && a[m] == b[m])
                --q;
        }
    }
    else if (p == r + 1)
    {
        int q = 0;
        //for (int i = ur - 1; i >= ul + 1; --i)
        int s = lower_bound(all(v[m]), ur) - v[m].begin();
        for (int ii = s - 1; ii >= 0; --ii)
        {
            int i = v[m][ii];

            if (!(ul < i && i < ur))
                continue;

            bool z = false;
            if (b[i] == a[p])
            {
                z = true;
                ++q;
            }
            if (ul < m && m < i && a[m] == b[m])
                ++q;
            dp[h] = max(dp[h], q + rec(l, m - 1, ul, i, m) + rec(m + 1, r, ul, i, m));
            if (ul < m && m < i && a[m] == b[m])
                --q;
        }
    }
    else
        assert(false);

    return dp[h];
}

int solv0()
{
    for (int l = 1; l <= n; ++l)
    {
        maxi[l][l] = l;
        for (int r = l + 1; r <= n; ++r)
        {
            maxi[l][r] = maxi[l][r - 1];
            if (a[r] > a[maxi[l][r]])
                maxi[l][r] = r;
        }
    }

    for (int i = 1; i <= n; ++i)
        v[i].clear();
    rec0(1, n, 0);

    dp = new int[M];
    for (int i = 0; i < M; ++i)
        dp[i] = -1;
    return rec(1, n, 0, n + 1, 0);
}

int p[N];
int solv2()
{
    for (int i = 1; i <= n; ++i)
    {
        p[i] = p[i - 1];
        if (a[i] == b[i])
            ++p[i];
    }

    ul[0] = 0;
    for (int i = 1; i <= n; ++i)
    {
        if (a[i] > b[i])
        {
            ul[i] = i;
        }
        else
        {
            ul[i] = ul[i - 1];
        }
    }
    ur[n + 1] = n + 1;
    for (int i = n; i >= 1; --i)
    {
        if (a[i] > b[i])
        {
            ur[i] = i;
        }
        else
        {
            ur[i] = ur[i + 1];
        }
    }

    int ans = 0;
    for (int i = 1; i <= n; ++i)
    {
        if (a[i] <= b[i])
        {
            if (p[ur[i] - 1] - p[ul[i]] > 0)
                ++ans;
        }
    }

    return ans;
}

map<int, int> mp;

int maxu[N * 4];
void ubd(int tl, int tr, int x, int y, int pos)
{
    if (tl == tr)
    {
        maxu[pos] = y;
        return;
    }
    int m = (tl + tr) / 2;
    if (x <= m)
        ubd(tl, m, x, y, pos * 2);
    else
        ubd(m + 1, tr, x, y, pos * 2 + 1);
    maxu[pos] = max(maxu[pos * 2], maxu[pos * 2 + 1]);
}

int qry(int tl, int tr, int l, int r, int pos)
{
    if (l > r)
        return 0;
    if (tl == l && tr == r)
        return maxu[pos];
    int m = (tl + tr) / 2;
    return max(qry(tl, m, l, min(m, r), pos * 2),
               qry(m + 1, tr, max(m + 1, l), r, pos * 2 + 1));
}

int solv4()
{
    for (int i = 1; i <= n; ++i)
        mp[a[i]] = i;

    for (int i = 1; i <= n; ++i)
    {
        if (mp.find(b[i]) == mp.end())
            continue;
        int x = mp[b[i]];
        if (ul[x] < i && i < ur[x])
        {
            ubd(1, n, x, qry(1, n, 1, x, 1) + 1, 1);
        }
    }
    return maxu[1];
}

void solv()
{
    cin >> n;
    for (int i = 1; i <= n; ++i)
        cin >> a[i];
    for (int i = 1; i <= n; ++i)
        cin >> b[i];

    bool z2 = true;
    for (int i = 1; i <= n; ++i)
    {
        if (b[i] != b[1])
        {
            z2 = false;
            break;
        }
    }

    if (z2)
    {
        cout << solv2() << "\n";
        return;
    }

    pre();

    if (n <= 5000)
    {
        cout << solv0() << "\n";
        return;
    }

    cout << solv4() << "\n";
}

int main()
{
    #ifdef SOMETHING
    freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    #endif // SOMETHING
    ios_base::sync_with_stdio(false), cin.tie(0);

    while (!isprime(M))
        ++M;

    /*int st = 100;
    while (st--)
    {
        n = rnf() % 100 + 1;
        for (int i = 1; i <= n; ++i)
        {
            a[i] = rnf() % 100 + 1;
        }
        b[1] = a[rnf() % n + 1];
        for (int i = 2; i <= n; ++i)
            b[i] = b[1];

        if (solv0() != solv2())
        {
            cout << "WA\n";
            return 0;
        }
    }
    cout << "OK\n";
    return 0;*/

    int tt = 1;
    //cin >> tt;
    while (tt--)
    {
        solv();
    }
    return 0;
}

Compilation message (stderr)

exam.cpp: In function 'int rec(int, int, int, int, int)':
exam.cpp:157:18: warning: variable 'z' set but not used [-Wunused-but-set-variable]
  157 |             bool z = false;
      |                  ^

• Subtask 1: 14 / 14
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 23 / 23
• Subtask 5: 16 / 16
• Subtask 6: 0 / 22