#include<bits/stdc++.h> using namespace std; #define ll long long int #define f(n,m) for(int i=n; i<m; ++i) #define fj(n,m) for(int j=n; j<m; ++j) #define sp " " #define rf(n,m) for(int i=n-1; i>=m; --i) #define all(v) v.begin(),v.end() #define srt(nums) sort(nums.begin(), nums.end()); #define mx_e(nums) *max_element(nums.begin(), nums.end()) #define mn_e(nums) *min_element(nums.begin(), nums.end()) ll mod = (ll)1e9+7; vector<bool> sieve(ll n) { vector<bool> isPrime(n + 1, true); isPrime[0] = isPrime[1] = false; for (ll i = 2; i * i <= n; ++i) { if (isPrime[i]) { for (ll j = i * i; j <= n; j += i) { isPrime[j] = false; } } } return isPrime; } ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// // int help(int i, int j, vector<vector<int>>&grid){ // if(i<0 or j<0 or i) // } void solve(){ int n, m; cin >> n >> m; vector<string> arr(n); for (int i = 0; i < n; ++i) { cin >> arr[i]; } vector<vector<int>> dist(n, vector<int>(m, INT_MAX)); queue<pair<int, int>> q; for (int i = 0; i < n; ++i) { for (int j = 0; j < m; ++j) { if (arr[i][j] == '1') { dist[i][j] = 0; q.push({i, j}); } } } while (!q.empty()) { int x = q.front().first; int y = q.front().second; q.pop(); int offset[] = {0, -1, 0 ,1, 0}; for (int i = 0; i < 4; ++i) { int nx = x + offset[i]; int ny = y + offset[i+1]; if (nx >= 0 && nx < n && ny >= 0 && ny < m && dist[nx][ny] == INT_MAX) { dist[nx][ny] = dist[x][y] + 1; q.push({nx, ny}); } } } int ans = 0; for (int i = 0; i < n; ++i) { for (int j = 0; j < m; ++j) { ans = max(ans, dist[i][j]); } } cout << ans << endl; } int main(){ int t; cin >> t; while(t--){ solve(); } return 0; } check this code and correct it

    int n, m;
    cin >> n >> m;
    vector<string> arr(n);
    for (int i = 0; i < n; ++i) {
        cin >> arr[i];
    }
    vector<vector<int>> dist(n, vector<int>(m, INT_MAX));
    queue<pair<int, int>> q;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            if (arr[i][j] == '1') {
                dist[i][j] = 0;
                q.push({i, j});
            }
        }
    }
    while (!q.empty()) {
        int x = q.front().first;
        int y = q.front().second;
        q.pop();

        int offset[] = {0, -1, 0 ,1, 0};
        for (int i = 0; i < 4; ++i) {
            int nx = x + offset[i];
            int ny = y + offset[i+1];
            if (nx >= 0 && nx < n && ny >= 0 && ny < m && dist[nx][ny] == INT_MAX) {
                dist[nx][ny] = dist[x][y] + 1;
                q.push({nx, ny});
            }
        }
    }
    int ans = 0;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            ans = max(ans, dist[i][j]);
        }
    }
    cout << ans << endl;

while(t--){
 solve();