Submission #521998

#	Time	Username	Problem	Language	Result	Execution time	Memory
521998		Monarchuwu	Dango Maker (JOI18_dango_maker)	C++17	0 / 100	105 ms	262148 KiB

dango_maker

#include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
typedef long long ll;
typedef vector<int> vi;

const int N = 3000 + 3, N2 = N * N, inf = 1e9 + 7;
int m, n;
char c[N][N];
vi vertexX;

int cnt, num[2][2][N];
vi g[N2 * 3 / 2];
void init_graph() {
    for (int i = 0; i < m; ++i) cin >> c[i];
    for (int i = 0; i < m; ++i)
        for (int j = 0; j < n; ++j) if (c[i][j] == 'G') {

            // check ngang
            if (j > 0 && j + 1 < n && c[i][j - 1] == 'R' && c[i][j + 1] == 'W') {
                num[0][1][j] = ++cnt;
                vertexX.push_back(num[0][1][j]);

                if (i > 0 && num[1][0][j + 1])
                    g[num[0][1][j]].push_back(num[1][0][j + 1]);
            }

            // check dọc
            if (i > 0 && i + 1 < m && c[i - 1][j] == 'R' && c[i + 1][j] == 'W') {
                num[1][1][j] = ++cnt;

                if (j + 1 < n && num[0][0][j + 1])
                    g[num[0][0][j + 1]].push_back(num[1][1][j]);
            }

            if (num[0][1][j] && num[1][1][j])
                g[num[0][1][j]].push_back(num[1][1][j]);

            copy(num[0][1], num[0][1] + n, num[0][0]);
            fill(num[0][1], num[0][1] + n, 0);

            copy(num[1][1], num[1][1] + n, num[1][0]);
            fill(num[1][1], num[1][1] + n, 0);
        }
}

int mat[N2], dist[N2];
bool bfs() {
    queue<int> q;
    dist[0] = inf;
    for (int i : vertexX)
        if (mat[i]) dist[i] = inf;
        else {
            dist[i] = 0;
            q.push(i);
        }

    while (!q.empty()) {
        int u = q.front(); q.pop();
        for (int v : g[u]) {
            if (dist[mat[v]] == inf) {
                dist[mat[v]] = dist[u] + 1;
                q.push(mat[v]);
            }
        }
    }
    return dist[0] != inf;
}

bool dfs(int u) {
    for (int v : g[u]) {
        if (!mat[v] || (dist[mat[v]] == dist[u] + 1 && dfs(mat[v]))) {
            mat[v] = u, mat[u] = v;
            dist[u] = inf;
            return true;
        }
    }
    dist[u] = inf;
    return false;
}

int hopcroft_karp() {
    int ans(0);
    while (bfs()) {
        for (int i : vertexX)
            if (!mat[i] && dfs(i)) ++ans;
    }
    return ans;
}

int main() {
    cin.tie(NULL)->sync_with_stdio(false);
    cin >> m >> n;
    init_graph();

    cout << cnt - hopcroft_karp() << '\n';
}
/**  /\_/\
 *  (= ._.)
 *  / >0  \>1
**/

• Subtask 1: 0 / 13
• Subtask 2: 0 / 20
• Subtask 3: 0 / 67