Submission #1228223

#	Time	Username	Problem	Language	Result	Execution time	Memory
1228223		RakhimovAmir	Building 4 (JOI20_building4)	C++20	0 / 100	1 ms	320 KiB

building4

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
inline void debugMode() {
    #ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
    #endif // ONLINE_JUDGE
}

void solve() {
    int n, inf = 1e9;
    cin >> n;
    int a[2 * n][2];
    int mn[2 * n][2], mx[2 * n][2];
    for (int i = 0; i < 2 * n; i++) {
        cin >> a[i][0];
        mn[i][0] = mn[i][1] = inf;
        mx[i][0] = mx[i][1] = -inf;
    }
    for (int i = 0; i < 2 * n; i++) {
        cin >> a[i][1];
    }
    mn[0][0] = 0;
    mn[0][1] = 1;
    mx[0][0] = 0;
    mx[0][1] = 1;
    for (int i = 1; i < 2 * n; i++) {
        for (int j = 0; j < 2; j++) {
            for (int g = 0; g < 2; g++) {
                if (a[i][j] < a[i - 1][g])
                    continue;
                mn[i][j] = min(mn[i][j], mn[i - 1][g] + j);
                mx[i][j] = max(mx[i][j], mx[i - 1][g] + j);
            }
            // cout << mn[i][j] << " " << mx[i][j] << " ";
        }
        // cout << "\n";
    }
    for (int z = 0; z < 2; z++) {
        if (mn[2 * n - 1][z] > n || mx[2 * n - 1][z] < n)
            continue;
        int now = z, need = n;
        vector<char> v;
        for (int i = 2 * n - 1; i >= 0; i--) {
            // cout << now << " " << need << " " << mn[i][now] << " " << mx[i][now] << "\n";
            if (mn[i][now] > need || mx[i][now] < need)
                now ^= 1;
            need -= now;
            v.push_back((now ? 'B' : 'A'));
        }
        reverse(v.begin(), v.end());
        for (auto i : v)
            cout << i;
        return;
    }
    cout << -1;
}

signed main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    debugMode();
    int $ = 1;
    // cin >> $;
    while ($--) {
        solve();
    }
}

Compilation message (stderr)

building4.cpp: In function 'void debugMode()':
building4.cpp:7:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    7 |     freopen("in.txt", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
building4.cpp:8:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    8 |     freopen("out.txt", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 11
• Subtask 2: 0 / 89