Submission #424524

#	Time	Username	Problem	Language	Result	Execution time	Memory
424524		Kharis228	Building 4 (JOI20_building4)	C++14	100 / 100	338 ms	48228 KiB

building4

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

#define chkmin(a, b) a = min(a, b);
#define chkmax(a, b) a = max(a, b)
//#define int long long
#define size(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define pii pair<int, int>
#define fi first
#define se second
#define pb emplace_back
#define mp make_pair

const int inf = 1e9;
const int max_n = 1e6 + 3;

int n;
int A[max_n], B[max_n];
pii dp[max_n][2];

void run() {
    cin >> n;
    n *= 2;
    for (int i = 0; i < n; ++i)
        cin >> A[i];
    for (int i = 0; i < n; ++i)
        cin >> B[i];

    for (int i = 0; i < n; ++i)
        dp[i][0] = dp[i][1] = mp(inf, -inf);
    dp[0][0] = mp(0, 0);
    dp[0][1] = mp(1, 1);

    for (int i = 0; i < n - 1; ++i) {
        for (int msk = 0; msk < 4; ++msk) {
            if (((msk & 1) ? B[i] : A[i]) <= (msk & 2 ? B[i + 1] : A[i + 1])) {
                chkmin(dp[i + 1][msk >> 1 & 1].fi, dp[i][msk & 1].fi);
                chkmax(dp[i + 1][msk >> 1 & 1].se, dp[i][msk & 1].se);
            }
        }
        ++dp[i + 1][1].fi;
        ++dp[i + 1][1].se;
    }

    //for (int i = 0; i < n; ++i)
    //    cout << dp[i][0].fi << " " << dp[i][0].se << "  " << dp[i][1].fi << " " << dp[i][1].se << endl;


    if ((dp[n - 1][0].fi > n / 2 || dp[n - 1][0].se < n / 2) && (dp[n - 1][1].fi > n / 2 || dp[n - 1][1].se < n / 2)) {
        cout << -1;
        return;
    }
    vector<int> res(n);
    int oth = n / 2;
    int lst = inf;
    for (int i = n - 1; i >= 0; --i) {
        if (dp[i][0].fi <= oth && dp[i][0].se >= oth && A[i] <= lst) lst = A[i];
        else {
            --oth;
            res[i] = 1;
            lst = B[i];
        }
    }

    for (int i : res)
        cout << char('A' + i);
    cout << endl;
}

signed main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#ifdef ahahaha
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    run();
}

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