remove_if (STL Samples)
在Visual C++說明如何使用 remove_if Standard Template Library (STL)函式。
template<class ForwardIterator, class Predicate> inline
ForwardIterator remove_if(
ForwardIterator First,
ForwardIterator Last,
Predicate Pred
)
備註
.gif "注意事項") 注意事項 |
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類別/參數名稱在原型不符合版本在標頭檔 (Header File)。修改部分以提高可讀性。 |
remove_if 演算法從範圍(First， Last)來移除所有項目該原因讓述詞傳回 true。它會傳回 Iterator 等於 Last -n，其中的是中的元素 n =數字移除。這個範圍中的最後一個項目具有 n 有效，但未指定的值。容器的大小會維持不變。
範例
// remove_if.cpp
// compile with: /EHsc
// Illustrates how to use the remove_if function.
//
// Functions:
// remove_if - remove all elements from the sequence that
// satisfies a predicate.
// bind2nd - Returns true for elements for which the condition is true
// begin - Returns an iterator that points to the first element in a
// sequence
// end - Returns an iterator that points one past the end of a sequence
//////////////////////////////////////////////////////////////////////
// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)
#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
using namespace std;
int main()
{
const int VECTOR_SIZE = 8 ;
// Define a template class vector of integers
typedef vector<int > IntVector ;
//Define an iterator for template class vector of integer
typedef IntVector::iterator IntVectorIt ;
IntVector Numbers(VECTOR_SIZE) ; //vector containing numbers
IntVectorIt start, end, it, last;
start = Numbers.begin() ; // location of first
// element of Numbers
end = Numbers.end() ; // one past the location
// last element of Numbers
//Initialize vector Numbers
Numbers[0] = 10 ;
Numbers[1] = 20 ;
Numbers[2] = 10 ;
Numbers[3] = 15 ;
Numbers[4] = 12 ;
Numbers[5] = 7 ;
Numbers[6] = 9 ;
Numbers[7] = 10 ;
cout << "Before calling remove_if" << endl ;
// print content of Numbers
cout << "Numbers { " ;
for(it = start; it != end; it++)
cout << *it << " " ;
cout << " }\n" << endl ;
// remove all elements from Numbers that <= 10
last = remove_if(start, end, bind2nd(less_equal<int>(), 10) ) ;
cout << "After calling remove_if" << endl ;
// print content of Numbers
cout << "Numbers { " ;
for(it = start; it != end; it++)
cout << *it << " " ;
cout << " }\n" << endl ;
//print number of elements removed from Numbers
cout << "Total number of elements removed from Numbers = "
<< end - last << endl ;
//print only the valid elements of Number
cout << "Valid elements of Numbers { " ;
for(it = start; it != last; it++)
cout << *it << " " ;
cout << " }\n" << endl ;
}
Output
Before calling remove_if
Numbers { 10 20 10 15 12 7 9 10 }
After calling remove_if
Numbers { 20 15 12 15 12 7 9 10 }
Total number of elements removed from Numbers = 5
Valid elements of Numbers { 20 15 12 }
需求
Header: <algorithm>