1162

class Solution {
public:
    int maxDistance(vector<vector<int>>& g, int steps = 0) {
        queue<pair<int, int>> q, q1;

        for(int i = 0; i < g.size(); ++i)
            for(int j = 0; j < g[i].size(); ++j)
                if(g[i][j] == 1)
                    q.push({ i - 1, j }), q.push({ i + 1, j }), q.push({ i, j - 1 }), q.push({ i, j + 1 });

        while(!q.empty()) {
            ++steps;
            while(!q.empty()){
                int i = q.front().first, j = q.front().second;
                q.pop();
                if(i >= 0 && j >= 0 && i < g.size() && j < g[i].size() && g[i][j] == 0) {
                    g[i][j] = steps;
                    q1.push({ i - 1, j }), q1.push({ i + 1, j }), q1.push({ i, j - 1 }), q1.push({ i, j + 1 });
                }
            }
            swap(q1, q);
        }

        return steps == 1 ? -1 : steps - 1;
    }
};