Submission #211624

#	Time	Username	Problem	Language	Result	Execution time	Memory
211624		kuroni	Building 4 (JOI20_building4)	C++17	100 / 100	322 ms	28140 KiB

building4

#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;

const int N = 500005;

int n, a[2 * N][2];
bool chk[2 * N][2];
string ans;
pair<int, int> r[2 * N][2];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n;
    for (int it = 0; it < 2; it++) {
        for (int i = 1; i <= 2 * n; i++) {
            cin >> a[i][it];
        }
    }
    chk[0][0] = true;
    for (int i = 1; i <= 2 * n; i++) {
        for (int it = 0; it < 2; it++) {
            for (int j = 0; j < 2; j++) {
                if (chk[i - 1][j] && a[i - 1][j] <= a[i][it]) {
                    if (!chk[i][it]) {
                        chk[i][it] = true;
                        r[i][it] = {r[i - 1][j].fi + it, r[i - 1][j].se + it};
                    } else {
                        r[i][it].fi = min(r[i][it].fi, r[i - 1][j].fi + it);
                        r[i][it].se = max(r[i][it].se, r[i - 1][j].se + it);
                    }
                }
            }
        }
    }
    for (int it = 0; it < 2; it++) {
        if (chk[2 * n][it] && r[2 * n][it].fi <= n && n <= r[2 * n][it].se) {
            for (int i = 2 * n, cur = n; i >= 1; i--) {
                ans.push_back('A' + it);
                cur -= it;
                for (int j = 0; j < 2; j++) {
                    if (chk[i - 1][j] && a[i - 1][j] <= a[i][it] && r[i - 1][j].fi <= cur && cur <= r[i - 1][j].se) {
                        it = j;
                        break;
                    }
                }
            }
            reverse(ans.begin(), ans.end());
            return cout << ans, 0;
        }
    }
    cout << -1;
}

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