nth_element (STL Samples)

說明如何使用 nth_element Visual C++ 標準樣板程式庫 (STL) 函式。

template<class RandomAccessIterator> inline
   void nth_element(
      RandomAccessIterator First,
      RandomAccessIterator Nth,
      RandomAccessIterator Last
   )

備註

注意事項
在原型中的類別/參數名稱不相符的標頭檔中的版本。某些已修改以提高可讀性。

nth_element演算法的分割區順序 [First...Last) 所參考的值在開次 n。 小於或等於值會放在值之前的所有項目，且大於值的所有項目會放置在序列中的值之後。 Nonpredicate 版本nth_element會使用運算子 < 進行比較。

範例

// nth_element.cpp
// compile with: /EHsc
// Illustrates how to use the nth_element function.
//
// Functions:
//   nth_element : Partition the elements in a sequence by its nth
//                 element.

// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)

#include <iostream>
#include <algorithm>
#include <functional>
#include <vector>

using namespace std ;

int main()
{
    const int VECTOR_SIZE = 8 ;

    // Define a template class vector of int
    typedef vector<int> IntVector ;

    //Define an iterator for template class vector of strings
    typedef IntVector::iterator IntVectorIt ;

    IntVector Numbers(VECTOR_SIZE) ;

    IntVectorIt start, end, it ;

    // Initialize vector Numbers
    Numbers[0] = 4 ;
    Numbers[1] = 10;
    Numbers[2] = 70 ;
    Numbers[3] = 30 ;
    Numbers[4] = 10;
    Numbers[5] = 69 ;
    Numbers[6] = 96 ;
    Numbers[7] = 100;

    start = Numbers.begin() ;   // location of first
                                // element of Numbers

    end = Numbers.end() ;       // one past the location
                                // last element of Numbers

    cout << "Before calling nth_element\n" << endl ;

    // print content of Numbers
    cout << "Numbers { " ;
    for(it = start; it != end; it++)
        cout << *it << " " ;
    cout << " }\n" << endl ;

    // partition the elements by the 4th element
    nth_element(start, start+4, end) ;

    cout << "After calling nth_element\n" << endl ;

    cout << "Numbers { " ;
    for(it = start; it != end; it++)
        cout << *it << " " ;
    cout << " }\n" << endl ;
}

Output

Before calling nth_element

Numbers { 4 10 70 30 10 69 96 100  }

After calling nth_element

Numbers { 4 10 10 30 69 70 96 100  }

需求

標頭: <algorithm>

請參閱

概念

標準樣板程式庫範例