foo.cc: In function 'void dfs(int, int, int)':
foo.cc:21:64: error: 'sea' was not declared in this scope
   21 |                 if(xi>=0&&yj>=0&&xi<=r-1&&yj<=c-1&&!v[xi][yj]&&sea[xi][yj]=='.') dfs(xi,yj,lens++);
      |                                                                ^~~

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