7576번: 토마토

#include<cstdio>

#include<queue>

using namespace std;

int box[1000][1000];

bool visit[1000][1000];

int m, n, x, y, mx;

queue<int> qx, qy;

int main()

{

scanf("%d %d", &m, &n);

for (int i = 0; i < n; ++i)

for (int j = 0; j < m; ++j)

{

scanf("%d", &box[i][j]);

if (box[i][j] == 1)

{

qx.push(j);

qy.push(i);

visit[i][j] = 1;

}

}

while (!qx.empty())

{

x = qx.front();

y = qy.front();

qx.pop();

qy.pop();

if(y>0)

if(!visit[y-1][x]++)

if (box[y - 1][x] == 0)

{

box[y - 1][x] = box[y][x] + 1;

mx = (mx > box[y - 1][x]) ? mx : box[y - 1][x];

qx.push(x);

qy.push(y - 1);

}

if (y<n-1)

if (!visit[y + 1][x]++)

if (box[y + 1][x] == 0)

{

box[y + 1][x] = box[y][x] + 1;

mx = (mx > box[y + 1][x]) ? mx : box[y + 1][x];

qx.push(x);

qy.push(y + 1);

}

if (x>0)

if (!visit[y][x - 1]++)

if (box[y][x - 1] == 0)

{

box[y][x - 1] = box[y][x] + 1;

mx = (mx > box[y][x - 1]) ? mx : box[y][x - 1];

qx.push(x - 1);

qy.push(y);

}

if (x<m-1)

if (!visit[y][x + 1]++)

if (box[y][x + 1] == 0)

{

box[y][x + 1] = box[y][x] + 1;

mx = (mx > box[y][x + 1]) ? mx : box[y][x + 1];

qx.push(x + 1);

qy.push(y);

}

}

for (int i = 0; i < n; ++i)

for (int j = 0; j < m; ++j)

if (box[i][j] == 0)

{

printf("-1");

return 1;

}

mx = (mx == 0) ? mx : mx - 1;

printf("%d", mx);

}