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7576.cpp
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7576.cpp
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// Authored by : BaaaaaaaaaaarkingDog
// Co-authored by : -
// http://boj.kr/ae38aa7eb7a44aca87e9d7928402d040
#include <bits/stdc++.h>
using namespace std;
#define X first
#define Y second
int board[1002][1002];
int dist[1002][1002];
int n,m;
int dx[4] = {1,0,-1,0};
int dy[4] = {0,1,0,-1};
int main(void){
ios::sync_with_stdio(0);
cin.tie(0);
cin >> m >> n;
queue<pair<int,int> > Q;
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
cin >> board[i][j];
if(board[i][j] == 1)
Q.push({i,j});
if(board[i][j] == 0)
dist[i][j] = -1;
}
}
while(!Q.empty()){
auto cur = Q.front(); Q.pop();
for(int dir = 0; dir < 4; dir++){
int nx = cur.X + dx[dir];
int ny = cur.Y + dy[dir];
if(nx < 0 || nx >= n || ny < 0 || ny >= m) continue;
if(dist[nx][ny] >= 0) continue;
dist[nx][ny] = dist[cur.X][cur.Y]+1;
Q.push({nx,ny});
}
}
int ans = 0;
for(int i = 0; i < n; i++){
for(int j = 0; j < m; j++){
if(dist[i][j] == -1){
cout << -1;
return 0;
}
ans = max(ans, dist[i][j]);
}
}
cout << ans;
}