Compilare: user.cpp: In function ‘void pairup(int, int)’: user.cpp:39:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (p + msk < r[v].size() && col[r[v][p + msk]] <= col[x]) ^ user.cpp: In function ‘int main()’: user.cpp:46:9: warning: unused variable ‘a’ [-Wunused-variable] int l, a, b; ^ user.cpp:46:12: warning: unused variable ‘b’ [-Wunused-variable] int l, a, b; ^