Submission #1287577

#	Time	Username	Problem	Language	Result	Execution time	Memory
1287577		adscoding	Building 4 (JOI20_building4)	C++20	0 / 100	1 ms	340 KiB

building4

#include <bits/stdc++.h>
#define all(x) x.begin(), x.end()
#define BIT(mask, x) ((mask >> (x)) & 1)
#define FOR(i, a, b) for (int i = a, _b = b; i <= _b; ++i)
#define FORD(i, a, b) for (int i = a, _b = b; i >= _b; --i)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

// -------------------------------------- CON CUA BO HCN --------------------------------------

const int maxn = 1e6 + 3;
int n, a[maxn], b[maxn];
pii dp[maxn][2];

// --------------------------------------------------------------------------------------------

pii merge(const pii &x, const pii &y)
{
    return make_pair(min(x.first, y.first), max(x.second, y.second));
}

bool check(const pii &x, int y)
{
    return y >= x.first && y <= x.second;
}

void solve()
{
    cin >> n;
    FOR(i, 1, n << 1) cin >> a[i];
    FOR(i, 1, n << 1) cin >> b[i];
    FOR(i, 1, n << 1)
    {
        FOR(j, 0, 1) dp[i][j] = {1e9 + 1, -1e9 - 1};

        if (a[i] > a[i - 1]) dp[i][0] = merge(dp[i][0], make_pair(dp[i - 1][0].first + 1, dp[i - 1][0].second + 1));
        if (a[i] > b[i - 1]) dp[i][0] = merge(dp[i][0], make_pair(dp[i - 1][1].first + 1, dp[i - 1][1].second + 1));
        if (b[i] > a[i - 1]) dp[i][1] = merge(dp[i][1], dp[i - 1][0]);
        if (b[i] > b[i - 1]) dp[i][1] = merge(dp[i][1], dp[i - 1][1]);
    }

    int type = -1;
    if (check(dp[n << 1][0], n)) type = 0;
    else if (check(dp[n << 1][1], n)) type = 1;
    else return cout << -1, void();

    string ans = "";

    int u = n;

    FORD(i, n << 1, 1)
    {
        if (type == 0)
        {
            ans += 'A';
            --u;
            if (a[i] > b[i - 1] && check(dp[i - 1][1], u)) type = 1;
        }
        else
        {
            ans += 'B';
            if (b[i] > a[i - 1] && check(dp[i - 1][0], u)) type = 0;
        }
    }

    reverse(all(ans));
    cout << ans;
}

signed main()
{
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    #define TASK "TEST"
    if (fopen(TASK".INP", "r"))
    {
        freopen(TASK".INP", "r", stdin);
        freopen(TASK".OUT", "w", stdout);
    }
    solve();
    return 0;
}

/* NOTES:
    Luon la mot doan lien tiep
*/

Compilation message (stderr)

building4.cpp: In function 'int main()':
building4.cpp:79:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   79 |         freopen(TASK".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
building4.cpp:80:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |         freopen(TASK".OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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