Compilare: user.cpp: In function ‘void backt(int, int)’: user.cpp:16:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<sol.size();j++) ^ user.cpp:20:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a[nod].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:46:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a[actual].size();i++) ^ user.cpp:58:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=sol.size()-nrsol;i<sol.size();i++) ^