Compilare: user.cpp: In function ‘int main()’: user.cpp:26:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<x[a].size();j++){ ^ user.cpp:19:27: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&n,&m); ^ user.cpp:21:43: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d%d",&v[i].st,&v[i].dr); ^