foo.cpp:12:10: error: ISO C++ forbids initialization of member 'len' [-fpermissive]
foo.cpp:12:10: error: making 'len' static [-fpermissive]
foo.cpp:12:10: error: ISO C++ forbids in-class initialization of non-const static member 'len'
foo.cpp: In function 'void bfs()':
foo.cpp:63:9: warning: unused variable 'ns' [-Wunused-variable]