Compilare: user.cpp: In function ‘void solve(int)’: user.cpp:90:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < a[A].size(); ++i) ^ user.cpp:54:9: warning: variable ‘last_node’ set but not used [-Wunused-but-set-variable] int last_node = 0, c; ^ user.cpp:54:24: warning: unused variable ‘c’ [-Wunused-variable] int last_node = 0, c; ^