部分排序 用于对整个容器内的范围进行排序。因此,如果我们想保持原始容器的完整性,只需将容器中已排序的子部分复制到另一个容器中,那么出于这个目的,我们可以使用 std::部分排序拷贝 .
null
就像std::partial_sort一样,partial_sort_copy()可以通过两种方式使用,如下所示:
- 使用 <:>
语法:
Template RandomAccessIterator partial_sort_copy (InputIterator first, InputIterator last, RandomAccessIterator result_first, RandomAccessIterator result_last); first: Input iterator to the first element in the container. last: Input iterator to the last element in the container. result_first: Random-Access iterator pointing to the initial position in the destination container. result_last: Random-Access iterator pointing to the final position in the destination container. Return Value: It returns an iterator pointing to the element that follows the last element written in the result sequence.
// C++ program to demonstrate the use of
// std::partial_sort_copy
#include <iostream>
#include <vector>
#include <algorithm>
using
namespace
std;
int
main()
{
vector<
int
> v = { 1, 1, 3, 10, 3, 3, 7, 7, 8 }, v1(3);
vector<
int
>::iterator ip;
// Using std::partial_sort_copy
std::partial_sort_copy(v.begin(), v.end(), v1.begin(), v1.end());
// Displaying the vector after applying
// std::partial_sort_copy
for
(ip = v1.begin(); ip != v1.end(); ++ip) {
cout << *ip <<
" "
;
}
return
0;
}
输出:
1 1 3
在这里,因为,我们声明v1的大小为3,所以其中只存储了三个元素。
- 通过使用预定义函数进行比较:
语法:
Template RandomAccessIterator partial_sort_copy (InputIterator first, InputIterator last, RandomAccessIterator result_first, RandomAccessIterator result_last, Compare comp); Here, first, last, result_first and result_last are the same as previous case. comp: Binary function that accepts two elements in the range as arguments, and returns a value convertible to bool. The value returned indicates whether the element passed as first argument is considered to go before the second in the specific strict weak ordering it defines. The function shall not modify any of its arguments. This can either be a function pointer or a function object. Return Value: It returns an iterator pointing to the element that follows the last element written in the result sequence.
// C++ program to demonstrate the use of
// std::partial_sort_copy
#include <iostream>
#include <algorithm>
#include <vector>
using
namespace
std;
// Defining the BinaryFunction
bool
comp(
int
a,
int
b)
{
return
(a < b);
}
int
main()
{
vector<
int
> v = { 1, 1, 3, 10, 3, 3, 7, 7, 8 }, v1(7);
vector<
int
>::iterator ip;
// Using std::partial_sort_copy
std::partial_sort_copy(v.begin(), v.end(), v1.begin(),
v1.end(), comp);
// Displaying the vector after applying
// std::partial_sort_copy
for
(ip = v1.begin(); ip != v1.end(); ++ip) {
cout << *ip <<
" "
;
}
return
0;
}
输出:
1 1 3 3 3 7 7
在哪里使用?
- 要复制排序范围,请执行以下操作: 因此,每当我们希望原始容器在排序后保持不变,并且部分_排序的结果存储在另一个容器中时,我们就可以使用这个。
// C++ program to demonstrate the use of
// std::partial_sort_copy
#include <iostream>
#include <vector>
#include <algorithm>
using
namespace
std;
int
main()
{
vector<
int
> v = { 100, 45, 78, 23, 220 }, v1(5);
vector<
int
>::iterator ip;
// Using std::partial_sort_copy
std::partial_sort_copy(v.begin(), v.end(), v1.begin(),
v1.end());
// Displaying the vectors after applying
// std::partial_sort_copy
cout <<
"v = "
;
for
(ip = v.begin(); ip != v.end(); ++ip) {
cout << *ip <<
" "
;
}
cout <<
"v1 = "
;
for
(ip = v1.begin(); ip != v1.end(); ++ip) {
cout << *ip <<
" "
;
}
return
0;
}
输出:
v = 100 45 78 23 220 v1 = 23 45 78 100 220
所以,这里v保持不变,它的排序形式存储在v1中。
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