Submission #648400

#	Time	Username	Problem	Language	Result	Execution time	Memory
648400		bebra	Retro (COCI17_retro)	C++17	46 / 100	184 ms	217868 KiB

retro

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

#define dbg(x) cerr << #x << ": " << x << endl;

const int INF = 1e9;
const int MAX_N = 300;
const int MAX_BALANCE = 300 / 2 + 5;
char grid[MAX_N][MAX_N];

int dp[MAX_N][MAX_N][MAX_BALANCE];
tuple<int, int, int> p[MAX_N][MAX_N][MAX_BALANCE];


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, m;
    cin >> n >> m;
    for (int i = 0; i < n; ++i) {
        string s;
        cin >> s;
        for (int j = 0; j < m; ++j) {
            grid[i][j] = s[j];
        }
    }
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            for (int k = 0; k < MAX_BALANCE; ++k) {
                dp[i][j][k] = -INF;
            }
        }
    }
    const int max_balance = n / 2 + 5;
    // moves (if possible):
    // (i - 1; j - 1)
    // (i - 1; j)
    // (i - 1; j + 1)
    //
    auto gen_moves = [&](int x, int y) -> vector<pair<int, int>> {
        vector<pair<int, int>> moves;
        if (y - 1 >= 0) {
            if (grid[x + 1][y - 1] != '*') {
                moves.emplace_back(x + 1, y - 1);
            }
        }
        if (y + 1 < m) {
            if (grid[x + 1][y + 1] != '*') {
                moves.emplace_back(x + 1, y + 1);
            }
        }
        if (grid[x + 1][y] != '*') {
            moves.emplace_back(x + 1, y);
        }
        return moves;
    };
    for (int j = 0; j < m; ++j) {
        if (grid[n - 1][j] == 'M') {
            dp[n - 1][j][0] = 0;
        }
    }
    for (int i = n - 2; i >= 0; --i) {
        for (int j = 0; j < m; ++j) {
            auto moves = gen_moves(i, j);
            for (int k = 0; k < max_balance; ++k) {
                for (const auto& [prev_i, prev_j] : moves) {
                    if (grid[i][j] == '.' || grid[i][j] == '*') {
                        if (dp[prev_i][prev_j][k] > dp[i][j][k]) {
                            dp[i][j][k] = dp[prev_i][prev_j][k];
                            p[i][j][k] = {prev_i, prev_j, k};
                        }
                    } else if (grid[i][j] == '(') {
                        if (k != 0 && dp[prev_i][prev_j][k - 1] + 1 > dp[i][j][k]) {
                            dp[i][j][k] = dp[prev_i][prev_j][k - 1] + 1;
                            p[i][j][k] = {prev_i, prev_j, k - 1};
                        }
                    } else if (grid[i][j] == ')') {
                        if (k + 1 < max_balance && dp[prev_i][prev_j][k + 1] + 1 > dp[i][j][k]) {
                            dp[i][j][k] = dp[prev_i][prev_j][k + 1] + 1;
                            p[i][j][k] = {prev_i, prev_j, k + 1};
                        }
                    }
                }
            }
        }
    }
    int max_len = 0;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            if (i == 0 || grid[i][j] == '*') {
                max_len = max(max_len, dp[i][j][0]);
            }
        }
    }
    string min_seq = "~";
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            if ((i == 0 || grid[i][j] == '*') && dp[i][j][0] == max_len) {
                string curr_seq;
                int curr_i = i;
                int curr_j = j;
                int curr_balance = 0;
                while (curr_i != n - 1) {
                    if (grid[curr_i][curr_j] == '(') {
                        curr_seq += '(';
                    } else if (grid[curr_i][curr_j] == ')') {
                        curr_seq += ')';
                    }
                    tie(curr_i, curr_j, curr_balance) = p[curr_i][curr_j][curr_balance];
                }
                reverse(curr_seq.begin(), curr_seq.end());
                min_seq = min(min_seq, curr_seq);
            }
        }
    }
    if (min_seq == "~") {
        min_seq = "";
    }
    cout << max_len << '\n';
    cout << min_seq << '\n';
    return 0;
}

• Subtask 1: 46 / 100