Doing a graph problem but it giving TLE I can't able to figure out why it is giving

Question Link - CodeChef | Competitive Programming | Participate & Learn

I am solving this problem with the help of BFS. But it is giving TLE. Can please help me to find what is the problem with my code.

int dir[4][2] = {{-1, 0}, {1, 0}, {0, 1}, {0, -1}};

bool isInside(int nx, int ny, int n, int m) {
    if(nx < 0 || nx >= n || ny < 0 || ny >= m) {
        return false;
    }
    return true;
}

int findIsland(int x, int y, int n, int m, vector<vector<int>> mat, vector<vector<bool>>& vis) {
    int count = 1;
    queue<pair<int, int>> q;
    q.push({x, y});
    vis[x][y] = true;
    while(!q.empty()) {
        pair<int, int> ele = q.front();
        q.pop();
        for(int i = 0; i < 4; i++) {
            int nx = ele.first + dir[i][0];
            int ny = ele.second + dir[i][1];
            if(isInside(nx, ny, n, m) && mat[nx][ny] == 1 && !vis[nx][ny]) {
                vis[nx][ny] = true;
                count++;
                q.push({nx, ny});
            }
        }
    }
    return count;
}

void solve() {
    int n, m;
    cin >> n >> m;
    vector<string> temp(n);
    for(int i = 0; i < n; i++) {
        cin >> temp[i];
    }
    //cout << n << " " << m << endl;
    vector<vector<int>> mat(n, vector<int>(m, 0));
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            mat[i][j] = temp[i][j] - '0';
        }
    }
    vector<int> arr;
    vector<vector<bool>> vis(n, vector<bool>(m, false));
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            if(mat[i][j] == 1 && vis[i][j] == false) {
                int island = findIsland(i, j, n, m, mat, vis);
                arr.push_back(island);
            }
        }
    }

    sort(arr.begin(), arr.end());
    reverse(arr.begin(), arr.end());
    int ans = 0;
    for(int i = 1; i < (int)arr.size(); i+=2) {
        ans += arr[i];
    }

    cout << ans << endl;
}