Submission #1262349

#	Time	Username	Problem	Language	Result	Execution time	Memory
1262349		icebear	Building 4 (JOI20_building4)	C++20	100 / 100	153 ms	25860 KiB

building4

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

typedef long long ll;
typedef pair<int, int> ii;
typedef pair<int, ii> iii;

template<class T>
    bool minimize(T &a, const T &b) {
        if (a > b) return a = b, true;
        return false;
    }

template<class T>
    bool maximize(T &a, const T &b) {
        if (a < b) return a = b, true;
        return false;
    }

#define FOR(i,a,b) for(int i=(a); i<=(b); ++i)
#define FORR(i,a,b) for(int i=(a); i>=(b); --i)
#define REP(i, n) for(int i=0; i<(n); ++i)
#define RED(i, n) for(int i=(n)-1; i>=0; --i)
#define MASK(i) (1LL << (i))
#define BIT(S, i) (((S) >> (i)) & 1)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define task "icebear"

const int MOD = 1e9 + 7;
const int inf = 1e9 + 27092008;
const ll INF = 1e18 + 27092008;
const int N = 1000000 + 5;
int n, a[2][N];
int f[N][2][2];

void init(void) {
    cin >> n;
    REP(i, 2) FOR(j, 1, 2 * n) cin >> a[i][j];
}

void process(void) {
    FOR(i, 0, 2 * n) FOR(j, 0, 1) {
        f[i][j][0] = inf;
        f[i][j][1] = -inf;
    }
    f[0][0][0] = f[0][0][1] = 0;
    f[0][1][0] = f[0][1][1] = 0;
    FOR(i, 0, 2 * n - 1) FOR(j, 0, 1) FOR(k, 0, 1) if (f[i][j][k] > -inf && f[i][j][k] < inf) {
        FOR(t, 0, 1) if (a[t][i + 1] >= a[j][i]) {
            minimize(f[i + 1][t][0], f[i][j][k] + (t == 0));
            maximize(f[i + 1][t][1], f[i][j][k] + (t == 0));
        }
    }
    cerr << f[2][0][1] << ' ' << f[2][0][0] << '\n';
    int mn = min(f[2*n][0][0], f[2*n][1][0]);
    int mx = max(f[2*n][0][1], f[2*n][1][1]);
    cerr << mn << ' ' << mx << '\n';
    if (mn <= n && n <= mx) {
        int cur = n;
        vector<char> res(2*n);
        int i = 2*n;
        while(i > 0) {
            if (f[i][0][0] <= cur && cur <= f[i][0][1] && (i == 2*n || a[0][i] <= a[(res[i] == 'A' ? 0 : 1)][i+1]))
                res[i-1] = 'A', cur--;
            else res[i-1] = 'B';
            i--;
        }
        for(auto &c : res) cout << c;
    } else cout << -1;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    int tc = 1;
//    cin >> tc;
    while(tc--) {
        init();
        process();
    }
    return 0;
}

Compilation message (stderr)

building4.cpp: In function 'int main()':
building4.cpp:81:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
building4.cpp:82:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   82 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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