C++ Tutorial/STL Algorithms Modifying sequence operations/stable partition — различия между версиями
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Текущая версия на 13:31, 25 мая 2010
Use stable_partition algorithms: preserving relative order in each group
<source lang="cpp">#include <algorithm>
- include <vector>
- include <string>
- include <iostream>
- include <iterator>
using namespace std; bool above40(int n) { return (n > 4); } int main() {
const int N = 7; int array0[N] = {5, 3, 1, 7, 6, 4, 2}; int array1[N]; copy(&array0[0], &array0[N], &array1[0]); ostream_iterator<int> out(cout, " "); cout << "Original sequence: "; copy(&array1[0], &array1[N], out); cout << endl; // Partition array1, putting numbers greater than 4 // first, followed by those less than or equal to 4, // preserving relative order in each group: int* split = stable_partition(&array1[0], &array1[N], above40); cout << "Result of stable partitioning: "; copy(&array1[0], split, out); cout << "| "; copy(split, &array1[N], out); cout << endl; return 0;
}</source>
Original sequence: 5 3 1 7 6 4 2 Result of stable partitioning: 5 7 6 | 3 1 4 2
Use stable_partition and partition
<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() {
vector<int> coll1; vector<int> coll2; INSERT_ELEMENTS(coll1,1,9); INSERT_ELEMENTS(coll2,1,9); PRINT_ELEMENTS(coll1,"coll1: "); PRINT_ELEMENTS(coll2,"coll2: "); cout << endl; // move all even elements to the front vector<int>::iterator pos1, pos2; pos1 = partition(coll1.begin(), coll1.end(), // range not1(bind2nd(modulus<int>(),2))); // criterion pos2 = stable_partition(coll2.begin(), coll2.end(), // range not1(bind2nd(modulus<int>(),2))); // crit. // print collections and first odd element PRINT_ELEMENTS(coll1,"coll1: "); cout << "first odd element: " << *pos1 << endl; PRINT_ELEMENTS(coll2,"coll2: "); cout << "first odd element: " << *pos2 << endl;
}</source>
coll1: 1 2 3 4 5 6 7 8 9 coll2: 1 2 3 4 5 6 7 8 9 coll1: 8 2 6 4 5 3 7 1 9 first odd element: 5 coll2: 2 4 6 8 1 3 5 7 9 first odd element: 1