unique_copy/unique_copy_if详解

unique_copy:在unique的基础上,不改变源容器,并将得到的结果复制给_Dest.

template<class _FwdIt,

         class_OutIt,

         class_Pr> inline

         _OutIt _Unique_copy(_FwdIt _First,_FwdIt _Last,

                   _OutIt _Dest, _Pr _Pred,forward_iterator_tag)

         {       // copy compressing pairs satisfying _Pred, forwarditerators

         _FwdIt _Firstb = _First;

         for(*_Dest++ = *_Firstb; ++_First != _Last; )

                   if(!_Pred(*_Firstb, *_First))

                            {       // copyunmatched

                            _Firstb = _First;

                            *_Dest++ = *_Firstb;

                            }

         return(_Dest);

         }

对应的一个函数:

template<class _FwdIt,

         class_OutIt,

         class_Pr> inline

         _OutIt _Unique_copy(_FwdIt _First,_FwdIt _Last,

                   _OutIt _Dest, _Pr _Pred,forward_iterator_tag)

         {       // copy compressing pairs satisfying _Pred, forwarditerators

         _FwdIt _Firstb = _First;

         for(*_Dest++ = *_Firstb; ++_First != _Last; )

                   if(!_Pred(*_Firstb, *_First))//循环体之所以比unique简单,原因在于,有额外的容器提供保存值.

                            {       // copyunmatched

                            _Firstb = _First;

                            *_Dest++ = *_Firstb;

                            }

         return(_Dest);

         }

举例:

1.       int main()

2.       {

3.       typedef vector<int>vecIntContains;

4.       vecIntContainsvecInt;

5.       vecInt.push_back(2 );

6.       vecInt.push_back(7 );

7.       vecInt.push_back(7 );

8.       vecInt.push_back(5 );

9.       vecInt.push_back(4 );

10.    vecInt.push_back(1 );

11.    vecInt.push_back(4 );

12.    vecInt.push_back(1 );

13.    vecIntContainsvecNew;

14.    unique_copy(vecInt.begin(),vecInt.end(),ostream_iterator<int>(cout," " ) );//left > right

15.     

16.    cout<<"\nunique second operator:\n";

17.    unique_copy(vecInt.begin(),vecInt.end() - 1,ostream_iterator<int>(cout," " ),greater<int>() );//left >right

18.    system( "pause" );

19.    return 0;

20.    }

21.     

这里需要注意的一个小问题是,14行返回值不是vector<int>::iterator.