蓝桥杯岛屿个数dfs（已找到bug）

#include <bits/stdc++.h>
#define endl "\n"
using namespace std;
int m, n;
int dx[4] = {0,-1,0,1};
int dy[4] = {-1,0,1,0};
 
int dxx[8] = {0,-1,0,1,-1,-1,1,1};
int dyy[8] = {-1,0,1,0,-1,1,-1,1};
 
int res = 0;
void dfs_road(vector<vector<char>> &grid,int x,int y,vector<vector<bool>> &visited)
{
  visited[x][y] = true;
  for(int i = 0;i < 4;i++)
  {
    int nextx = x + dx[i];
    int nexty = y + dy[i];
    if(nextx < 0 || nexty < 0 || nextx >= grid.size() || nexty >= grid[0].size()) continue;
    if(!visited[nextx][nexty] && grid[nextx][nexty] == '1')
    {
      visited[nextx][nexty] = true;
      dfs_road(grid,nextx,nexty,visited);
    }
  }
}
//
void dfs_sea(vector<vector<char>> &grid,int x,int y,vector<vector<bool>> &visited)
{
  visited[x][y] = true;
  for(int i = 0;i < 8;i++)
  {
    int nextx = x + dxx[i];
    int nexty = y + dyy[i];
    if(nextx < 0 || nexty < 0 || nextx >= grid.size() || nexty >= grid[0].size()) continue;
    if(!visited[nextx][nexty] && grid[nextx][nexty] == '1')
    {
      visited[nexty][nexty] = true;
      dfs_road(grid,nextx,nexty,visited);
      res++;
    }
    if(!visited[nextx][nexty] && grid[nextx][nexty] == '0')
    {
      visited[nextx][nexty] = true;
      dfs_sea(grid,nextx,nexty,visited);
    }
  }
}
void solve()
{
  cin >> m >>n;
  res = 0;
  vector<vector<char>> grid(m,vector<char>(n));
  vector<vector<bool>> visited = vector<vector<bool>>(m,vector<bool>(n,false));
  for(int i = 0;i < m;i++)
  {
    for(int j = 0;j < n;j++)
    {
      cin >> grid[i][j];
    }
  }
  //从边缘遍历岛屿
  for(int i = 0;i < m;i++)
  {
    if(!visited[i][0] && grid[i][0] == '1')
    {
      dfs_road(grid,i,0,visited);
      res++;
    }
    if(!visited[i][n - 1] && grid[i][n - 1] == '1')
    {
      dfs_road(grid,i,n - 1,visited);
      res++;
    }
  }
  for(int j = 0;j < n;j++)
  {
    if(!visited[0][j] && grid[0][j] == '1') 
    {
      dfs_road(grid,0,j,visited);
      res++;
    }
    if(!visited[m - 1][j] && grid[m - 1][j] == '1')
    {
      dfs_road(grid,m - 1,j,visited);
      res++;
    }
  }
  //从边缘的海遍历 遇见没有遍历过的陆地再做dfs
  for(int i = 0;i < m;i++)
  {
    if(!visited[i][0] && grid[i][0] == '0')
    {
      dfs_sea(grid,i,0,visited);
    }
    //
    if(!visited[i][n - 1] && grid[i][n - 1] == '0')
    {
      dfs_sea(grid,i,n - 1,visited);
    }
  }
  for(int j = 0;j < n;j++)
  {
    if(!visited[0][j] && grid[0][j] == '0') 
    {
      dfs_sea(grid,0,j,visited);
    }
    //
    if(!visited[m - 1][j] && grid[m - 1][j] == '0')
    {
      dfs_sea(grid,m - 1,j,visited);
    }
  }
  cout << res << endl;
}
signed main()
{
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  cin >> t;
  while(t--)
  solve();
  return 0;
}