C++/STL Algorithms Sorting/partial sort
Содержание
The generic partial_sort algorithms with predicate
<source lang="cpp">
- include <vector>
- include <algorithm>
- include <iostream>
- include <iterator>
using namespace std; class comp_last {
public: bool operator()(int x, int y) const // Compare x and y based on their last base-10 digits: { return x 10; }
}; int main() {
const int N = 20; vector<int> vector0; for (int i = 0; i < N; ++i) vector0.push_back(i); vector<int> vector1 = vector0; ostream_iterator<int> out(cout, " "); cout << "Before sorting:\n"; copy(vector1.begin(), vector1.end(), out); cout << endl; sort(vector1.begin(), vector1.end(), comp_last()); cout << "After sorting by last digits with sort:\n"; copy(vector1.begin(), vector1.end(), out); cout << endl << endl; vector1 = vector0; reverse(vector1.begin(), vector1.end()); cout << "Before sorting:\n"; copy(vector1.begin(), vector1.end(), out); cout << endl << endl; partial_sort(vector1.begin(), vector1.begin() + 5,vector1.end(), comp_last()); cout << "After sorting with partial_sort to get 5 values with smallest last d
igits:\n";
copy(vector1.begin(), vector1.end(), out); cout << endl << endl; return 0;
}
/*
Before sorting: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 After sorting by last digits with sort: 10 0 11 1 12 2 13 3 4 14 5 15 6 16 7 17 8 18 9 19 Before sorting: 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 After sorting with partial_sort to get 5 values with smallest last digits: 10 0 11 1 12 19 18 17 16 15 9 8 7 6 5 4 14 13 3 2
*/ </source>
Use partial_sort to sort all elements
<source lang="cpp">
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference" * by Nicolai M. Josuttis, Addison-Wesley, 1999 * * (C) Copyright Nicolai M. Josuttis 1999. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */
- include <iostream>
- include <vector>
- include <deque>
- include <list>
- include <set>
- include <map>
- include <string>
- include <algorithm>
- include <iterator>
- include <functional>
- include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by * - all elements of the collection coll * - separated by spaces */
template <class T> inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="") {
typename T::const_iterator pos; std::cout << optcstr; for (pos=coll.begin(); pos!=coll.end(); ++pos) { std::cout << *pos << " "; } std::cout << std::endl;
} /* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection * - NOTE: NO half-open range */
template <class T> inline void INSERT_ELEMENTS (T& coll, int first, int last) {
for (int i=first; i<=last; ++i) { coll.insert(coll.end(),i); }
} using namespace std; int main() {
deque<int> coll; INSERT_ELEMENTS(coll,3,7); INSERT_ELEMENTS(coll,2,6); INSERT_ELEMENTS(coll,1,5); PRINT_ELEMENTS(coll); // sort all elements partial_sort (coll.begin(), // beginning of the range coll.end(), // end of sorted range coll.end()); // end of full range PRINT_ELEMENTS(coll);
} /* 3 4 5 6 7 2 3 4 5 6 1 2 3 4 5 1 2 2 3 3 3 4 4 4 5 5 5 6 6 7
*/ </source>
Use partial_sort to sort until the first five elements are sorted
<source lang="cpp">
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference" * by Nicolai M. Josuttis, Addison-Wesley, 1999 * * (C) Copyright Nicolai M. Josuttis 1999. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */
- include <iostream>
- include <vector>
- include <deque>
- include <list>
- include <set>
- include <map>
- include <string>
- include <algorithm>
- include <iterator>
- include <functional>
- include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by * - all elements of the collection coll * - separated by spaces */
template <class T> inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="") {
typename T::const_iterator pos; std::cout << optcstr; for (pos=coll.begin(); pos!=coll.end(); ++pos) { std::cout << *pos << " "; } std::cout << std::endl;
} /* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection * - NOTE: NO half-open range */
template <class T> inline void INSERT_ELEMENTS (T& coll, int first, int last) {
for (int i=first; i<=last; ++i) { coll.insert(coll.end(),i); }
} using namespace std; int main() {
deque<int> coll; INSERT_ELEMENTS(coll,3,7); INSERT_ELEMENTS(coll,2,6); INSERT_ELEMENTS(coll,1,5); PRINT_ELEMENTS(coll); // sort until the first five elements are sorted partial_sort (coll.begin(), // beginning of the range coll.begin()+5, // end of sorted range coll.end()); // end of full range PRINT_ELEMENTS(coll);
} /* 3 4 5 6 7 2 3 4 5 6 1 2 3 4 5 1 2 2 3 3 7 6 5 5 6 4 4 3 4 5
*/ </source>
Use partial_sort with custom function to sort inversely until the first five elements are sorted
<source lang="cpp">
/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference" * by Nicolai M. Josuttis, Addison-Wesley, 1999 * * (C) Copyright Nicolai M. Josuttis 1999. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */
- include <iostream>
- include <vector>
- include <deque>
- include <list>
- include <set>
- include <map>
- include <string>
- include <algorithm>
- include <iterator>
- include <functional>
- include <numeric>
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by * - all elements of the collection coll * - separated by spaces */
template <class T> inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="") {
typename T::const_iterator pos; std::cout << optcstr; for (pos=coll.begin(); pos!=coll.end(); ++pos) { std::cout << *pos << " "; } std::cout << std::endl;
} /* INSERT_ELEMENTS (collection, first, last)
* - fill values from first to last into the collection * - NOTE: NO half-open range */
template <class T> inline void INSERT_ELEMENTS (T& coll, int first, int last) {
for (int i=first; i<=last; ++i) { coll.insert(coll.end(),i); }
} using namespace std; int main() {
deque<int> coll; INSERT_ELEMENTS(coll,3,7); INSERT_ELEMENTS(coll,2,6); INSERT_ELEMENTS(coll,1,5); PRINT_ELEMENTS(coll); // sort inversely until the first five elements are sorted partial_sort (coll.begin(), // beginning of the range coll.begin()+5, // end of sorted range coll.end(), // end of full range greater<int>()); // sorting criterion PRINT_ELEMENTS(coll);
}
/*
3 4 5 6 7 2 3 4 5 6 1 2 3 4 5 7 6 6 5 5 2 3 3 4 4 1 2 3 4 5
*/ </source>