Submission #466697

#	Time	Username	Problem	Language	Result	Execution time	Memory
466697		Valaki2	Exam (eJOI20_exam)	C++14	39 / 100	61 ms	2508 KiB

exam

#include <bits/stdc++.h>
using namespace std;

int n;
vector<int> a;
vector<int> b;

void solve_bf() {
    set<int> a_set;
    vector<bool> possible(1 + n, false);
    for(int i = 1; i <= n; ++i) a_set.insert(a[i]);
    for(int i = 1; i <= n; ++i) if(a_set.count(b[i])) possible[i] = true;
    int ans = 0;
    vector<bool> cur(1 + n, false);
    for(int mask = 0; mask < (1 << n); ++mask) {
        bool ok = true;
        for(int i = 0; i < n; ++i) {
            if(mask & (1 << i)) {
                cur[i + 1] = true;
                if(!possible[i + 1]) ok = false;
            } else {
                cur[i + 1] = false;
            }
        }
        if(!ok) continue;
        for(int i = 1; i <= n; ++i) {
            if(!cur[i]) continue;
            bool done = false;
            for(int j = i; j >= 1; --j) {
                if(a[j] > b[i] || (cur[j] && b[j] < b[i])) break;
                if(a[j] == b[i]) {
                    done = true;
                    break;
                }
            }
            for(int j = i; j <= n; ++j) {
                if(a[j] > b[i] || (cur[j] && b[j] < b[i])) break;
                if(a[j] == b[i]) {
                    done = true;
                    break;
                }
            }
            if(!done) ok = false;
        }
        if(ok) ans = max(ans, __builtin_popcount(mask));
    }
    cout << ans << "\n";
}

void solve_bequal() {
    int x = b[1];
    int last = 0;
    bool ok = false;
    int ans = 0;
    a.push_back(x + 1);
    for(int i = 1; i <= (n + 1); ++i) {
        if(a[i] > x) {
            if(ok) {
                ans += i - last - 1;
                ok = false;
            }
            last = i;
        } else if(a[i] == x) {
            ok = true;
        }
    }
    cout << ans << "\n";
}

void solve_astrictlyincreasing() {
    vector<int> dp(1 + n, 0);
    for(int i = 1; i <= n; ++i) {
        vector<int> cnt_left(1 + i + 1, 0);
        // vector<int> cnt_right(1 + i + 1, 0);
        for(int j = 1; j <= i; ++j) {
            cnt_left[j] = cnt_left[j - 1];
            if(b[j] == a[i]) ++cnt_left[j];
        }
        /*for(int j = i; j >= 1; --j) {
            cnt_right[j] = cnt_right[j + 1];
            if(b[j] == a[i]) ++cnt_right[j];
        }*/
        int maxi = 0;
        for(int j = 1; j <= i; ++j) {
            maxi = max(maxi, dp[j] - cnt_left[j]);
            dp[j] = max(dp[j], maxi + cnt_left[j]);
        }
    }
    cout << dp[n] << "\n";
}

void solve() {
    cin >> n;
    a.assign(1 + n, 0);
    b.assign(1 + n, 0);
    for(int i = 1; i <= n; ++i) cin >> a[i];
    for(int i = 1; i <= n; ++i) cin >> b[i];
    set<int> b_set;
    for(int i = 1; i <= n; ++i) {
        b_set.insert(b[i]);
    }
    if(n <= 10) {
        solve_bf();
    } else if(b_set.size() == 1) {
        solve_bequal();
    } else {
        solve_astrictlyincreasing();
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}

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