Eroare de compilare: In file included from /usr/include/c++/4.8/algorithm:62:0, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:64, from user.cpp:1: /usr/include/c++/4.8/bits/stl_algo.h: In instantiation of ‘_RandomAccessIterator std::__unguarded_partition(_RandomAccessIterator, _RandomAccessIterator, const _Tp&) [with _RandomAccessIterator = Mat*; _Tp = Mat]’: /usr/include/c++/4.8/bits/stl_algo.h:2307:70: required from ‘_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = Mat*]’ /usr/include/c++/4.8/bits/stl_algo.h:2338:54: required from ‘void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = Mat*; _Size = int]’ /usr/include/c++/4.8/bits/stl_algo.h:5475:36: required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = Mat*]’ user.cpp:70:28: required from here /usr/include/c++/4.8/bits/stl_algo.h:2269:19: error: passing ‘const Mat’ as ‘this’ argument of ‘bool Mat::operator<(const Mat&)’ discards qualifiers [-fpermissive] while (__pivot < *__last) ^ user.cpp: In function ‘void read()’: user.cpp:52:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &n, &m, &d); ^ user.cpp:56:40: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &a[++ len].val); ^