洛谷g++出问题了？

#include <cstdio>
#include <cstring>

const int maxn = 1005;
bool graph[maxn][maxn];
int vis[maxn][maxn];
int cnt[1000005];

int n, m;
char ch;
int nowID = 1;

int i2, j2;

const int di[4] = {0, 1, 0, -1};
const int dj[4] = {1, 0, -1, 0};

void dfs(int i = 0, int j = 0, int depth = 0)
{
	vis[i][j] = nowID;
	cnt[nowID]++;
	for (int k = 0; k < 4; ++k)
	{
		i2 = i + di[k];
		j2 = j + dj[k];
		if (i2 >= 0 && j2 >= 0 && i2 < n && j2 < n && !vis[i2][j2] && (graph[i][j] != graph[i2][j2]))
			dfs(i2, j2, depth + 1);
	}
	if (!depth)
		nowID++;
}

int main()
{
	scanf("%d%d", &n, &m);
	getchar();
	for (int i = 0; i < n; ++i)
	{
		for (int j = 0; j < n; ++j)
		{
			ch = getchar();
			if (ch == '0')
				graph[i][j] = false;
			else
				graph[i][j] = true;
		}
		getchar();
	}

	for (int i = 0; i < n; ++i)
		for (int j = 0; j < n; ++j)
			if (!vis[i][j])
				dfs(i, j);
	for (int k = 0; k < m; ++k)
	{
		int i, j;
		scanf("%d%d", &i, &j);
		printf("%d\n", cnt[vis[i - 1][j - 1]]);
	}
	return 0;
}

8 4
10010011
01100100
10010011
01011011
10001000
00011011
00101000
00000010
1 2
8 6
6 2
4 3

0
12
5
7

25
19
1
25