20分RE，数组貌似没有越界

#include <iostream>
#define endl "\n"
using namespace std;

int main()
{
	ios::sync_with_stdio(false);
	int dx[]={1, 1, 1, 0, -1, -1, 1, 0};
	int dy[]={1, 0, -1, -1, -1, 0, 1, 1};
	int n, m;
	cin >> n >> m;
	char ch[n+2][m+2];
	for (int i=1; i<=n; i++)
		for (int j=1; j<=m; j++)
			cin >> ch[i][j];
	for (int i=0; i<=n+1; i++)
		ch[i][0]=ch[i][m+1]='?';
	for (int i=0; i<=m+1; i++)
		ch[0][i]=ch[n+1][0]='?';
	for (int i=1; i<=n; i++)
	{
		for (int j=1; j<=m; j++)
		{
			if (ch[i][j]=='*')
			{
				cout << '*';
				continue;
			}
			int cnt=0;
			for (int k=1; k<=8; k++)
				if (ch[i+dx[k]][j+dy[k]]=='*')
					cnt++;
			cout << cnt;			
		}
		cout << endl;
	}
	return 0;
}