Compilare: user.cpp: In function ‘void back(int, int, int)’: user.cpp:13:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<L[p][i].size();j++) ^ user.cpp:21:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0;j<L[p][x[i]].size();j++){ ^ user.cpp:30:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0;j<L[p][rest].size();j++) ^ user.cpp: In function ‘int main()’: user.cpp:64:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (t=0;t<L[i][j].size();t++) ^