Compilare: user.cpp: In function ‘int main()’: user.cpp:47:31: warning: operation on ‘i’ may be undefined [-Wsequence-point] for(i=1;i<=n;a[i].second=i++) scanf("%ld",&a[i].first); ^ user.cpp:61:32: warning: format ‘%ld’ expects argument of type ‘long int’, but argument 2 has type ‘std::vector<long int>::size_type {aka unsigned int}’ [-Wformat=] printf("%ld\n",ans.size()*2); ^ user.cpp:62:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<ans.size();i++) printf("P %ld\nP %ld\n",ans[i]-1,ans[i]); ^ user.cpp:43:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("permsort2.in","r",stdin); ^ user.cpp:44:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("permsort2.out","w",stdout); ^ user.cpp:46:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld",&n); AIB Aib(n); ^ user.cpp:47:59: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(i=1;i<=n;a[i].second=i++) scanf("%ld",&a[i].first); ^