max_element

尋找最大項目第一次出現在排程的準則可能是由二進位述詞指定的所指定的範圍內。

template<class ForwardIterator>
   ForwardIterator max_element(
      ForwardIterator _First, 
      ForwardIterator _Last
   );
template<class ForwardIterator, class BinaryPredicate>
   ForwardIterator max_element(
      ForwardIterator _First, 
      ForwardIterator _Last, 
      BinaryPredicate _Comp
   );

參數

• _First
  處理順向 Iterator 的第一個項目的位置。最大的項目所要搜尋的範圍。

• _Last
  處理順向的 Iterator 超過最後一個項目的位置是在最大項目所要搜尋的範圍。

• _Comp
  定義感受遠遠之使用者定義的述詞函式物件哪個項目大於另一個執行個體。這個二進位述詞會採用兩個引數，而且應傳回 true ，當第一個項目小於則為第二個項目和 false 小於時。

傳回值

處理順向 Iterator 的最大項目的第一次出現的位置在搜尋到的範圍。

備註

參考的範圍必須是有效的，任何指標必須 dereferenceable，而且每一個序列中最後一個位置開始可取得的會增加。

複雜的線性:(_Last – _First) – 1 次比較對於非空的範圍是必要的。

範例

// alg_max_element.cpp
// compile with: /EHsc
#include <vector>
#include <set>
#include <algorithm>
#include <iostream>
#include <ostream>

using namespace std;
class CInt;
ostream& operator<<( ostream& osIn, const CInt& rhs );

class CInt
{
public:
   CInt( int n = 0 ) : m_nVal( n ){}
   CInt( const CInt& rhs ) : m_nVal( rhs.m_nVal ){}
   CInt& operator=( const CInt& rhs ) {m_nVal = 
   rhs.m_nVal; return *this;}
   bool operator<( const CInt& rhs ) const 
      {return ( m_nVal < rhs.m_nVal );}
   friend ostream& operator<<( ostream& osIn, const CInt& rhs );

private:
   int m_nVal;
};

inline ostream& operator<<(ostream& osIn, const CInt& rhs)
{
   osIn << "CInt( " << rhs.m_nVal << " )"; 
   return osIn;
}

// Return whether modulus of elem1 is greater than modulus of elem2
bool mod_lesser ( int elem1, int elem2 )
{
   if ( elem1 < 0 ) 
      elem1 = - elem1;
   if ( elem2 < 0 ) 
      elem2 = - elem2;
   return elem1 < elem2;
};

int main( )
{
   // Searching a set container with elements of type CInt 
   // for the maximum element 
   CInt c1 = 1, c2 = 2, c3 = -3;
   set<CInt> s1;
   set<CInt>::iterator s1_Iter, s1_R1_Iter, s1_R2_Iter;
   
   s1.insert ( c1 );
   s1.insert ( c2 );
   s1.insert ( c3 );

   cout << "s1 = (";
   for ( s1_Iter = s1.begin( ); s1_Iter != --s1.end( ); s1_Iter++ )
      cout << " " << *s1_Iter << ",";
   s1_Iter = --s1.end( );
   cout << " " << *s1_Iter << " )." << endl;

   s1_R1_Iter = max_element ( s1.begin ( ) , s1.end ( ) );

   cout << "The largest element in s1 is: " << *s1_R1_Iter << endl;
   cout << endl;

   // Searching a vector with elements of type int for the maximum
   // element under default less than & mod_lesser binary predicates
   vector <int> v1;
   vector <int>::iterator v1_Iter, v1_R1_Iter, v1_R2_Iter;

   int i;
   for ( i = 0 ; i <= 3 ; i++ )
   {
      v1.push_back( i );
   }

   int ii;
   for ( ii = 1 ; ii <= 4 ; ii++ )
   {
      v1.push_back( - 2 * ii );
   }
   
   cout << "Vector v1 is ( " ;
   for ( v1_Iter = v1.begin( ) ; v1_Iter != v1.end( ) ; v1_Iter++ )
      cout << *v1_Iter << " ";
   cout << ")." << endl;

   v1_R1_Iter = max_element ( v1.begin ( ) , v1.end ( ) );
   v1_R2_Iter = max_element ( v1.begin ( ) , v1.end ( ), mod_lesser);

   cout << "The largest element in v1 is: " << *v1_R1_Iter << endl;
   cout << "The largest element in v1 under the mod_lesser"
        << "\n binary predicate is: " << *v1_R2_Iter << endl;
}

Output

s1 = ( CInt( -3 ), CInt( 1 ), CInt( 2 ) ).
The largest element in s1 is: CInt( 2 )

Vector v1 is ( 0 1 2 3 -2 -4 -6 -8 ).
The largest element in v1 is: 3
The largest element in v1 under the mod_lesser
 binary predicate is: -8

需求

標題: <algorithm>

命名空間: std

請參閱

參考

Nonpredicate Version of max_element

Predicate Version of max_element

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