Submission #1071710

#	Time	Username	Problem	Language	Result	Execution time	Memory
1071710		manhlinh1501	Building 4 (JOI20_building4)	C++17	100 / 100	312 ms	96308 KiB

building4

#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
using pii = pair<int, int>;
const int MAXN = 1e6 + 5;
#define prev ___prev
const int oo32 = 1e9 + 5;

int N;
int a[MAXN];
int b[MAXN];
int ans[MAXN];

template <class T1, class T2>
bool maximize(T1 &a, T2 b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <class T1, class T2>
bool minimize(T1 &a, T2 b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

namespace subtask {
    const int MAXN = 4e3 + 5;
    bool dp[MAXN][MAXN][2];
    array<int, 3> prev[MAXN][MAXN][2];

    void solution() {
        dp[0][0][0] = dp[0][0][1] = true;
        for (int i = 1; i <= 2 * N; i++) {
            if (a[i - 1] <= a[i]) {
                for (int j = 0; j <= N; j++) {
                    if (dp[i - 1][j][0]) {
                        dp[i][j][0] = true;
                        prev[i][j][0] = {i - 1, j, 0};
                    }
                }
            }
            if (b[i - 1] <= a[i]) {
                for (int j = 0; j <= N; j++) {
                    if (dp[i - 1][j][1]) {
                        dp[i][j][0] = true;
                        prev[i][j][0] = {i - 1, j, 1};
                    }
                }
            }
            if (a[i - 1] <= b[i]) {
                for (int j = 1; j <= N; j++) {
                    if (dp[i - 1][j - 1][0]) {
                        dp[i][j][1] = true;
                        prev[i][j][1] = {i - 1, j - 1, 0};
                    }
                }
            }
            if (b[i - 1] <= b[i]) {
                for (int j = 1; j <= N; j++) {
                    if (dp[i - 1][j - 1][1]) {
                        dp[i][j][1] = true;
                        prev[i][j][1] = {i - 1, j - 1, 1};
                    }
                }
            }
        }
        if (dp[2 * N][N][0]) {
            array<int, 3> cur = {2 * N, N, 0};
            while (cur[0]) {
                ans[cur[0]] = cur[2];
                cur = prev[cur[0]][cur[1]][cur[2]];
            }
            for (int i = 1; i <= 2 * N; i++)
                cout << (ans[i] ? 'B' : 'A');
        } else if (dp[2 * N][N][1]) {
            array<int, 3> cur = {2 * N, N, 1};
            while (cur[0]) {
                ans[cur[0]] = cur[2];
                cur = prev[cur[0]][cur[1]][cur[2]];
            }
            for (int i = 1; i <= 2 * N; i++)
                cout << (ans[i] ? 'B' : 'A');
        } else
            cout << -1;
    }
}

int dp[MAXN][2][2];
array<int, 3> prev[MAXN][2][2];

void update_minn(array<int, 3> a, array<int, 3> b, int x) {
    if (minimize(dp[a[0]][a[1]][a[2]], dp[b[0]][b[1]][b[2]] + x))
        prev[a[0]][a[1]][a[2]] = b;
}

void update_maxx(array<int, 3> a, array<int, 3> b, int x) {
    if (maximize(dp[a[0]][a[1]][a[2]], dp[b[0]][b[1]][b[2]] + x))
        prev[a[0]][a[1]][a[2]] = b;
}

signed main() {
#define TASK "code"

    if (fopen(TASK ".inp", "r")) {
        freopen(TASK ".inp", "r", stdin);
        freopen(TASK ".out", "w", stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin >> N;
    for (int i = 1; i <= 2 * N; i++)
        cin >> a[i];
    for (int i = 1; i <= 2 * N; i++)
        cin >> b[i];
    for (int i = 1; i <= 2 * N; i++) {
        dp[i][0][0] = dp[i][1][0] = oo32;
        dp[i][0][1] = dp[i][1][1] = -oo32;
    }
    for (int i = 1; i <= 2 * N; i++) {
        if (a[i - 1] <= a[i] and (dp[i - 1][0][0] != oo32 and dp[i - 1][0][1] != -oo32)) {
            update_minn({i, 0, 0}, {i - 1, 0, 0}, 1);
            update_maxx({i, 0, 1}, {i - 1, 0, 1}, 1);
        }
        if (b[i - 1] <= a[i] and (dp[i - 1][1][0] != oo32 and dp[i - 1][1][1] != -oo32)) {
            update_minn({i, 0, 0}, {i - 1, 1, 0}, 1);
            update_maxx({i, 0, 1}, {i - 1, 1, 1}, 1);
        }

        if (a[i - 1] <= b[i] and (dp[i - 1][0][0] != oo32 and dp[i - 1][0][1] != -oo32)) {
            update_minn({i, 1, 0}, {i - 1, 0, 0}, 0);
            update_maxx({i, 1, 1}, {i - 1, 0, 1}, 0);
        }

        if (b[i - 1] <= b[i] and (dp[i - 1][1][0] != oo32 and dp[i - 1][1][1] != -oo32)) {
            update_minn({i, 1, 0}, {i - 1, 1, 0}, 0);
            update_maxx({i, 1, 1}, {i - 1, 1, 1}, 0);
        }
    }
    int OK = -1;
    if(dp[2 * N][0][0] <= N and N <= dp[2 * N][0][1])
        OK = 1;
    else if(dp[2 * N][1][0] <= N and dp[2 * N][1][1])
        OK = 0;
    else return cout << -1, 0;
    ans[2 * N] = OK;
    int cnt = N - OK;
    for(int i = 2 * N - 1; i >= 1; i--) {
        int last = (ans[i + 1] == 0 ? b[i + 1] : a[i + 1]);
        if(dp[i][0][0] <= cnt and cnt <= dp[i][0][1] and cnt > 0 and a[i] <= last) {
            OK = 1;
            cnt--;
        } else OK = 0;
        ans[i] = OK;
    }
    for(int i = 1; i <= 2 * N; i++)
        cout << (ans[i] ? 'A' : 'B');
    return (0 ^ 0);
}

Compilation message (stderr)

building4.cpp: In function 'int main()':
building4.cpp:111:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  111 |         freopen(TASK ".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
building4.cpp:112:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  112 |         freopen(TASK ".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

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