Submission #639708

#	Time	Username	Problem	Language	Result	Execution time	Memory
639708		two_sides	T-Covering (eJOI19_covering)	C++17	100 / 100	114 ms	23448 KiB

covering

#include <bits/stdc++.h>

using namespace std;

const int dx[] = {-1, 1, 0, 0};
const int dy[] = {0, 0, -1, 1};

vector<vector<int>> a, col;
vector<vector<int>> dp[2];
queue<pair<int, int>> que;
int n, m;

bool inside(int x, int y) {
    return x >= 0 && x < n && y >= 0 && y < m;
}

void impossible() {
    cout << "No\n"; exit(0);
}

void place(int i, int j, int d) {
    for (int k = 0; k < 4; k++)
        if (k != d) {
            int x = i + dx[k], y = j + dy[k];
            if (!inside(x, y) || col[x][y])
                impossible();
            col[x][y] = 2; que.emplace(x, y);
        }
    col[i][j] = 2;
}

void bfs() {
    int i, j;
    while (que.size()) {
        tie(i, j) = que.front(); que.pop();
        for (int k = 0; k < 4; k++) {
            int x = i + dx[k], y = j + dy[k];
            if (inside(x, y) && abs(col[x][y]) == 1)
                place(x, y, k ^ 1);
        }
    }
}

void dfs(int i, int j, int p) {
    col[i][j] = -1;
    dp[0][i][j] = dp[1][i][j] = -1e18;
    for (int k = 0; k < 4; k++) {
        if (k == p) continue;
        int x = i + dx[k] * 2, y = j + dy[k] * 2;
        if (!inside(x, y)) continue;
        if (col[x][y] == -1) {
            place(i, j, k); bfs();
        }
        if (col[x][y] == 1) dfs(x, y, k ^ 1);
    }
    for (int d = 0; d < 4; d++) {
        int tmp = a[i][j];
        for (int k = 0; k < 4; k++)
            if (k == d) {
                int x = i + dx[k] * 2, y = j + dy[k] * 2;
                if (k != p && inside(x, y))
                    tmp += max(dp[0][x][y], dp[1][x][y]);
            } else {
                tmp += a[i + dx[k]][j + dy[k]];
                int x = i + dx[k] * 2, y = j + dy[k] * 2;
                if (k != p && inside(x, y))
                    tmp += dp[0][x][y];
            }
        dp[d != p][i][j] = max(dp[d != p][i][j], tmp);
    }
    
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin >> n >> m;
    a.resize(n); col.resize(n);
    dp[0].resize(n); dp[1].resize(n);
    for (int i = 0; i < n; i++) {
        a[i].resize(m); col[i].resize(m);
        dp[0][i].resize(m); dp[1][i].resize(m);
        for (int &x : a[i]) cin >> x;
    }
    for (int i = 0; i < n; i++) {
        que.emplace(i, -1); que.emplace(i, m);
    }
    for (int j = 0; j < m; j++) {
        que.emplace(-1, j); que.emplace(n, j);
    }
    int k; cin >> k;
    while (k--) {
        int x, y; cin >> x >> y;
        if (col[x][y]) impossible();
        col[x][y] = 1; que.emplace(x, y);
    }
    for (int i = 1; i < n; i++)
        for (int j = 0; j < m; j++) {
            if (col[i][j] != 1) continue;
            if (j > 0 && col[i - 1][j - 1] == 1) {
                place(i, j, 0);
                place(i - 1, j - 1, 1);
            }
            if (j + 1 < m && col[i - 1][j + 1] == 1) {
                place(i, j, 0);
                place(i - 1, j + 1, 1);
            }
        }
    bfs(); int res = 0;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            if (col[i][j] == 1) {
                dfs(i, j, -1);
                if (col[i][j] == -1)
                    res += dp[1][i][j];
            }
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            if (col[i][j] == 2) res += a[i][j];
    cout << res;
}

Compilation message (stderr)

covering.cpp: In function 'void dfs(int, int, int)':
covering.cpp:46:33: warning: overflow in conversion from 'double' to '__gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type' {aka 'int'} changes value from '-1.0e+18' to '-2147483648' [-Woverflow]
   46 |     dp[0][i][j] = dp[1][i][j] = -1e18;
      |                                 ^~~~~

• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 15 / 15
• Subtask 6: 20 / 20
• Subtask 7: 30 / 30