Sokkelo

input/code.cpp: In function 'void set_io(std::__cxx11::string)':
input/code.cpp:19:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen((filename + ".in").c_str(), "r", stdin);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
input/code.cpp:20:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
         freopen((filename + ".out").c_str(), "w", stdout);
         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define fi first
#define se second
#define sz size
#define rsz resize
#define ii pair<int,int>
#define vi vector<int>
#define vvi vector<vector<int>>

void set_io(string filename = "") {
    ios::sync_with_stdio(0);
    cin.tie(0);

    if (filename != "") {
        freopen((filename + ".in").c_str(), "r", stdin);
        freopen((filename + ".out").c_str(), "w", stdout);
    }
}

int H, W, dx[] {-1, 0, 1 ,0}, dy[] {0, -1, 0, 1};
char grid[1005][1005];
ii j, k;
bool vis[1005][1005];

int dist(ii a, ii b) {
    return abs(a.fi - b.fi) + abs(a.se - b.se);
}

int main() {
	set_io("");

    cin >> H >> W;

    for (int y = 0; y < H; y++)
        for (int x = 0; x < W; x++) {
            cin >> grid[x][y];
            if (grid[x][y] == 'A') j = {x, y};
            else if (grid[x][y] == 'B') k = {x, y};
        }

    queue<ii> q;
    q.push(j);

    int sd = INT_MAX;
    ii cp;
    while (!q.empty()) {
        auto [x, y] = q.front();
        q.pop();

        if (vis[x][y]) continue;
        vis[x][y] = true;

        for (int d = 0; d < 4; d++) {
            int nx = x + dx[d],
            ny = y + dy[d];

            if (nx < 0 || nx >= W || ny < 0 || ny >= H || grid[nx][ny] != '.' ||
                vis[nx][ny])
                continue;
            
            int cd = dist({nx, ny}, k);
            if (cd < sd) {
                sd = cd;
                cp = ii(nx, ny);
            }
            q.push({nx, ny});
        }
    }

    grid[cp.fi][cp.se] = 'A';
    q = queue<ii>();
    q.push(k);

    while (!q.empty()) {
        auto [x, y] = q.front();
        q.pop();

        if (vis[x][y]) continue;
        vis[x][y] = true;

        for (int d = 0; d < 4; d++) {
            int nx = x + dx[d],
            ny = y + dy[d];

            if (nx < 0 || nx >= W || ny < 0 || ny >= H || grid[nx][ny] != '.' ||
                vis[nx][ny])
                continue;

            int cd = dist({nx, ny}, cp);
            if (cd < sd) 
                sd = cd;
            
            q.push({nx, ny});
        }
    }

    cout << sd << endl;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 2

Verdict: ACCEPTED

Test 5

Group: 2

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 1, 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 1, 2

Verdict: WRONG ANSWER

Test 11

Group: 2

Verdict: WRONG ANSWER

Test 12

Group: 1, 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 1, 2

Verdict: ACCEPTED

Test 15

Group: 2

Verdict: ACCEPTED

Test 16

Group: 2

Verdict: ACCEPTED

Test 17

Group: 2

Verdict: ACCEPTED