hackathon: "the xiaolin"

#include <bits/stdc++.h>
using namespace std;
constexpr char BARRIER = '#';
int n, m;
vector<vector<char>> board;
vector<vector<int>> dis;
constexpr int NR_DIRS = 4, dirI[] = {0, 0, 1, -1}, dirJ[] = {1, -1, 0, 0};
unordered_map<int, int> fr;

void read() {
    cin >> n >> m;
    board.resize(n + 3, vector<char>(m + 3, BARRIER));
    dis.resize(n + 3, vector<int>(m + 3, INT_MAX));
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            cin >> board[i][j];
        }
    }
}

void lee() {
    queue<pair<int, int>> q;
    q.emplace(1, 1);
    dis[1][1] = 0;
    while (!q.empty()) {
        const auto &[i, j] = q.front();
        q.pop();
        for (int dir = 0; dir < NR_DIRS; dir++) {
            int newI = i + dirI[dir];
            int newJ = j + dirJ[dir];
            if (board[newI][newJ] != BARRIER && dis[newI][newJ] > dis[i][j] + 1) {
                dis[newI][newJ] = dis[i][j] + 1;
                q.emplace(newI, newJ);
            }
        }
    }
}

void cnt() {
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if ((i == 1 && j == 1) || (i == n && j == m) || board[i][j] == BARRIER) {
                continue;
            }
            fr[dis[i][j]]++;
        }
    }
}

void getAns() {
    int ans = INT_MAX;
    if (dis[n][m] == INT_MAX) {
        ans = 0;
    } else {
        for (const auto &it : fr) {
            ans = min(ans, it.second);
        }
    }
    cout << ans << endl;
}

signed main() {
    read();
    lee();
    cnt();
    getAns();
    return 0;
}