Compilare: user.cpp: In function ‘void print()’: user.cpp:17:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v.size(); ++i) ~~^~~~~~~~~~ user.cpp: In function ‘bool backtrack(int, int)’: user.cpp:43:9: warning: unused variable ‘res’ [-Wunused-variable] bool res = backtrack(pos + 1, n); ^~~ user.cpp:45:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: At global scope: user.cpp:9:13: warning: ‘test’ defined but not used [-Wunused-variable] static bool test = false; ^~~~