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POC++ Reversely sort characters in a string
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copied!<p>There are tons of codes that sort an array of strings lexicographically but I can't find one that does sorting characters in ONE string reverse lexicographically. So far I discovered that using <code>std::sort()</code> in <code><algorithm></code> might be the closest candidate.</p> <p>This is what I tried:</p> <pre><code>template <typename T> class ReverseComparator{ bool operator()(T l, T r){return !(l < r);} }; //.....later std::sort(str.begin(), str.end(), comparator); </code></pre> <p>Here's the question: how can I initialize my comparator so that it can compare the characters in the string? I tried <code>ReverseComparator<char> comparator</code> but compiler throws a ton of error msg. <a href="http://ideone.com/ulB623_" rel="nofollow">gcc-4.5.1 showed these errors</a>:</p> <pre><code>In file included from /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/algorithm:63:0, from prog.cpp:1: prog.cpp: In function 'void std::__insertion_sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]': /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2192:4: instantiated from 'void std::__final_insertion_sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5252:4: instantiated from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' prog.cpp:12:49: instantiated from here prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2125:4: error: within this context prog.cpp: In function 'void std::__heap_select(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]': /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5100:7: instantiated from 'void std::partial_sort(_RAIter, _RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2297:8: instantiated from 'void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Size = int, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5250:4: instantiated from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' prog.cpp:12:49: instantiated from here prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1914:2: error: within this context prog.cpp: In function 'void std::__move_median_first(_Iterator, _Iterator, _Iterator, _Compare) [with _Iterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]': /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2260:7: instantiated from '_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2302:62: instantiated from 'void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Size = int, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5250:4: instantiated from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' prog.cpp:12:49: instantiated from here prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:108:7: error: within this context prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:110:4: error: within this context /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2260:7: instantiated from '_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2302:62: instantiated from 'void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Size = int, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5250:4: instantiated from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' prog.cpp:12:49: instantiated from here prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:112:9: error: within this context prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:115:12: error: within this context prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:117:12: error: within this context prog.cpp: In function '_RandomAccessIterator std::__unguarded_partition(_RandomAccessIterator, _RandomAccessIterator, const _Tp&, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Tp = char, _Compare = ReverseComparator<char>]': /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2261:78: instantiated from '_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2302:62: instantiated from 'void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Size = int, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5250:4: instantiated from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' prog.cpp:12:49: instantiated from here prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2229:4: error: within this context prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2232:4: error: within this context prog.cpp: In function 'void std::__unguarded_linear_insert(_RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]': /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2133:6: instantiated from 'void std::__insertion_sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2192:4: instantiated from 'void std::__final_insertion_sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5252:4: instantiated from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' prog.cpp:12:49: instantiated from here prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2083:7: error: within this context In file included from /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:62:0, from /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/algorithm:63, from prog.cpp:1: prog.cpp: In function 'void std::__adjust_heap(_RandomAccessIterator, _Distance, _Distance, _Tp, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Distance = int, _Tp = char, _Compare = ReverseComparator<char>]': /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_heap.h:434:4: instantiated from 'void std::make_heap(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1912:7: instantiated from 'void std::__heap_select(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5100:7: instantiated from 'void std::partial_sort(_RAIter, _RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2297:8: instantiated from 'void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Size = int, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5250:4: instantiated from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' prog.cpp:12:49: instantiated from here prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_heap.h:303:4: error: within this context prog.cpp: In function 'void std::__push_heap(_RandomAccessIterator, _Distance, _Distance, _Tp, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Distance = int, _Tp = char, _Compare = ReverseComparator<char>]': /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_heap.h:316:7: instantiated from 'void std::__adjust_heap(_RandomAccessIterator, _Distance, _Distance, _Tp, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Distance = int, _Tp = char, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_heap.h:434:4: instantiated from 'void std::make_heap(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:1912:7: instantiated from 'void std::__heap_select(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5100:7: instantiated from 'void std::partial_sort(_RAIter, _RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:2297:8: instantiated from 'void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Size = int, _Compare = ReverseComparator<char>]' /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_algo.h:5250:4: instantiated from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<char*, std::basic_string<char> >, _Compare = ReverseComparator<char>]' prog.cpp:12:49: instantiated from here prog.cpp:6:11: error: 'bool ReverseComparator<T>::operator()(T, T) [with T = char]' is private /usr/lib/gcc/i686-pc-linux-gnu/4.5.1/../../../../include/c++/4.5.1/bits/stl_heap.h:180:7: error: within this context </code></pre>

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