Submission #55129546

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Source Code Expand

// {{{
#include <bits/stdc++.h>
using namespace std;
using LL = long long;
using vi = vector<int>;
using pii = pair<int, int>;
#define sz(x) (int)((x).size())
#define all(x) (x).begin(), (x).end()
#define clr(a, b) memset(a, b, sizeof(a))
#define debug(x...)
#define debug_arr(x...)
#ifdef LOCAL
#include "prettyprint.hpp"
#endif
// }}}

// clang-format off
template <class T = LL>
struct fenwick {
    int _n; vector<T> arr;
    fenwick() = default;
    fenwick(int size) { init(size); }
    void init(int size) { _n = size + 2, arr.assign(_n + 1, INT_MIN); }
    void set(int k, T num) { for (++k; k < _n; k += k & (-k)) arr[k] = max(arr[k], num); }

    T mx(int k) const {
        if (k < 0) return INT_MIN;
        T s = INT_MIN;
        for (++k; k; k -= k & (-k)) s = max(s, arr[k]);
        return s;
    }
};
// clang-format on

unordered_map<int, int> cord_mp, rev_mp;
void compress(vi a)
{
    cord_mp.clear(), rev_mp.clear();
    vi d = a;
    sort(all(d));
    d.resize(unique(all(d)) - d.begin());
    for (int i = 0; i < sz(d); ++i) cord_mp[d[i]] = i + 1, rev_mp[i + 1] = d[i];
}

const int N = 2e5 + 10;
int n;
int oa[N], a[N];

// int dp[2][N][N];

int main()
{
#ifdef LOCAL
    freopen("in", "r", stdin);
    // freopen("out", "w", stdout);
#endif

    while (cin >> n)
    {
        vi aa;

        for (int i = 1; i <= n; ++i)
        {
            cin >> a[i];
            oa[i] = a[i];
            aa.push_back(a[i]);
            aa.push_back(a[i] + 1);
        }

        if (n <= 2)
        {
            cout << n << endl;
            continue;
        }

        // if (n > 100)
        //{
        // assert(0);
        // continue;
        //}

        compress(aa);
        cord_mp[0] = 0, rev_mp[0] = 0;
        for (int i = 1; i <= n; ++i) a[i] = cord_mp[a[i]];

        int tot = cord_mp.size();

        fenwick<int> dp0(tot + 1), dp1(tot + 1);
        dp0.set(0, 0), dp1.set(0, 0);

        // clr(dp, -0x3f);
        // dp[0][0][0] = 0;
        // dp[1][0][0] = 0;

        for (int i = 1; i <= n; i++)
        {
            // dp0
            int maxv1 = 0;
            int q = dp0.mx(a[i] - 1) + 1;
            maxv1 = max(maxv1, q);

            // dp1 a[i] not change
            int maxv2 = 0;
            int q1 = dp0.mx(a[i] - 1) + 1;
            int q2 = dp1.mx(a[i] - 1) + 1;
            maxv2 = max(maxv2, q1);
            maxv2 = max(maxv2, q2);

            // dp1 set a[i] as a[i-1]+1
            int change_idx = cord_mp[oa[i - 1] + 1];
            int maxv3 = 0;
            int q3 = dp0.mx(change_idx - 1) + 1;
            maxv3 = max(maxv3, q3);

            dp0.set(a[i], maxv1);
            dp1.set(a[i], maxv2);
            dp1.set(change_idx, maxv3);

            // debug(i, q, q1, q2, maxv1, maxv2);

            /*
            // dp0
            for (int j = 0; j <= tot; j++)
            {
                int maxv11 = dp[0][i - 1][j];
                if (j == a[i])
                {
                    for (int k = 0; k < j; k++)
                    {
                        maxv11 = max(maxv11, dp[0][i - 1][k] + 1);
                    }
                }
                dp[0][i][j] = maxv11;
            }

            // dp1
            for (int j = 0; j <= tot; j++)
            {
                // int maxv22 = dp[1][i - 1][j];
                int maxv22 = max(dp[1][i - 1][j], dp[0][i - 1][j]);

                // change a[i] to any but not necessary
                // for (int k = 0; k < j; k++)
                //{
                // maxv22 = max(maxv22, dp[0][i - 1][k] + 1);
                //}

                int change_idx = 0;
                if (i > 1) change_idx = cord_mp[oa[i - 1] + 1];
                if (j == change_idx)
                {
                    for (int k = 0; k < j; k++)
                    {
                        // debug("here", dp[0][i - 1][change_idx]);
                        maxv22 = max(maxv22, dp[0][i - 1][k] + 1);
                    }
                }

                // debug(i, j, change_idx);
                if (j == a[i])
                {
                    for (int k = 0; k < j; k++)
                    {
                        maxv22 = max(maxv22, dp[1][i - 1][k] + 1);
                    }
                }
                dp[1][i][j] = maxv22;
            }
            */
        }

        int ans = dp0.mx(tot);
        ans = max(ans, dp1.mx(tot));
        cout << ans << endl;

        // int ans2 = 0;
        // for (int j = 0; j <= tot; j++)
        //{
        // ans2 = max(ans2, dp[0][n][j]);
        // ans2 = max(ans2, dp[1][n][j]);
        //}
        // assert(ans2 > 0);
        // cout << ans2 << endl;
    }

    return 0;
}

Submission Info

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