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#ifndef ALGORITHMS_H
#define ALGORITHMS_H 1
#include <algorithm>
#include <iterator>
#include <utility>
#include <vector>
/** Apply function f to each element in the range [first, last) for
* which the predicate p is true.
*/
template<class It, class Function, class Pred>
Function for_each_if(It first, It last, Function f, Pred p)
{
for (; first != last; ++first)
if (p(*first))
f(*first);
return f;
}
/** Copies each element in the range [first, last) into the range
* starting at result for which the predicate p is true. */
template<class InputIt, class OutputIt, class Pred>
OutputIt copy_if(InputIt first, InputIt last, OutputIt result,
Pred pred)
{
for (; first != last; ++first) {
if (pred(*first)) {
*result = *first;
++result;
}
}
return result;
}
/** Sorts the elements in the range [first,last) ordered by the value
* returned by the unary function op, which is called once for each
* element in the range [first,last). The copy constructor of the
* value_type of It is not used.
*/
template <class It, class Op>
void sort_by_transform(It first, It last, Op op)
{
typedef typename std::iterator_traits<It>::difference_type
size_type;
typedef typename Op::result_type key_type;
size_type n = last - first;
std::vector< std::pair<key_type, size_type> > keys;
keys.reserve(n);
for (It it = first; it != last; ++it)
keys.push_back(std::make_pair(op(*it), it - first));
sort(keys.begin(), keys.end());
for (size_type i = 0; i < n; i++) {
size_type j = keys[i].second;
while (j < i)
j = keys[j].second;
if (i != j)
std::swap(first[i], first[j]);
keys[i].second = j;
}
}
#endif
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