Compilare: user.cpp: In function ‘void backt(int, int)’: user.cpp:18:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i==n) ^ user.cpp:21:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k=1;k<=n;k++) ^ user.cpp: In function ‘int main()’: user.cpp:40:54: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(f>>x) {nr++; v[i].push_back(x); if(nr==i) {nr=0; i++;}} ^ user.cpp:50:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[n].size();i++) ^ user.cpp:53:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[k].size();i++) ^ user.cpp:58:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[n].size();i++) ^ user.cpp:64:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[k].size()&&ok;i++) ^