Submission #211920

#	Time	Username	Problem	Language	Result	Execution time	Memory
211920		WLZ	Building 4 (JOI20_building4)	C++14	100 / 100	469 ms	121776 KiB

building4

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
using namespace std;

const int INF = 0x3f3f3f3f;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    vector< vector<int> > a(2, vector<int>(2 * n + 1));
    for (int i = 0; i < 2; i++) {
        for (int j = 1; j <= 2 * n; j++) {
            cin >> a[i][j];
        }
    }
    vector< vector<int> > dp_r(2 * n + 1, vector<int>(2, -1));
    vector< vector<int> > dp_l(2 * n + 1, vector<int>(2, INF));
    dp_r[0][0] = dp_r[0][1] = dp_l[0][0] = dp_l[0][1] = 0;
    for (int i = 0; i < 2 * n; i++) {
        for (int j = 0; j < 2; j++) {
            if (dp_r[i][j] == -1) {
                continue;
            }
            if (a[j][i] <= a[0][i + 1]) {
                dp_r[i + 1][0] = max(dp_r[i + 1][0], dp_r[i][j] + 1);
                dp_l[i + 1][0] = min(dp_l[i + 1][0], dp_l[i][j] + 1);
            }
            if (a[j][i] <= a[1][i + 1]) {
                dp_r[i + 1][1] = max(dp_r[i + 1][1], dp_r[i][j]);
                dp_l[i + 1][1] = min(dp_l[i + 1][1], dp_l[i][j]);
            }
        }
    }
    int cur;
    if (dp_r[2 * n][0] >= n && dp_l[2 * n][0] <= n) {
        cur = 0;
    } else if (dp_r[2 * n][1] >= n && dp_l[2 * n][1] <= n) {
        cur = 1;
    } else {
        cout << -1 << '\n';
        return 0;
    }
    string ans = "";
    for (int i = 2 * n, cnt = n; i >= 1; i--) {
        if (cur == 0) {
            ans += 'A';
            cnt--;   
        } else {
            ans += 'B';
        }
        if (a[0][i - 1] <= a[cur][i] && dp_r[i - 1][0] >= cnt && dp_l[i - 1][0] <= cnt) {
            cur = 0;
        } else {
            cur = 1;
        }
    }
    reverse(ans.begin(), ans.end());
    cout << ans << '\n';
    return 0;
}

• Subtask 1: 11 / 11
• Subtask 2: 89 / 89