find/find_if詳解

find/find_if:
函數功能:返回元素值為_Val的迭代器
template<class _InIt,
         class_Ty> inline
         _InIt find(_InIt _First, _InIt _Last, const _Ty& _Val)
         {       // find first matching _Val
         _DEBUG_RANGE(_First, _Last);
         return(_Rechecked(_First,
                   _Find(_Unchecked(_First),_Unchecked(_Last), _Val)));
         }
         // TEMPLATEFUNCTION find
         template<class _InIt,
         class_Ty> inline
                   _InIt _Find(_InIt _First,_InIt _Last, const _Ty& _Val)
         {       // find first matching _Val
                   for(; _First != _Last; ++_First)
                            if (*_First == _Val)
                                     break;
                   return(_First);
         }
注意:
◆  函數返回值的區間在[begin,end]之間.因此當我們調用這個函數的時候,我們應將返回的值與end比較.
◆  順序容器不要使用算法庫的find操作,而應該使用其本身提供的find.(原因很簡單,自己肯定最了解自己)
◆  同樣最好不要改變區間的值 www.2cto.com
find_if函數實現:
                   //TEMPLATE FUNCTION find_if
template<class _InIt,
         class_Pr> inline
         _InIt _Find_if(_InIt _First, _InIt_Last, _Pr _Pred)
         {       // find first satisfying _Pred
         for (;_First != _Last; ++_First)
                   if(_Pred(*_First))//這裡使用單個參數的bool型函數:bool(*pFun)( T )
                            break;
         return(_First);
         }
 
template<class _InIt,
         class_Pr> inline
         _InIt find_if(_InIt _First, _InIt_Last, _Pr _Pred)
         {       // find first satisfying _Pred
         _DEBUG_RANGE(_First, _Last);
         _DEBUG_POINTER(_Pred);
         return(_Rechecked(_First,
                   _Find_if(_Unchecked(_First),_Unchecked(_Last), _Pred)));
         }
函數功能:返回使得_Pred為true的迭代器.
舉例:
template<typenameT>
bool equal_ten( T _value )
{
         return_value == 3;
}
int main()
{
         vector<int>vecInt;
         vecInt.push_back( 2 );
         vecInt.push_back( 5 );
         vecInt.push_back( 7 );
         vecInt.push_back( 3 );
         vecInt.push_back( 2 );
         vecInt.push_back( 4 );
         vecInt.push_back( 3 );
         vecInt.push_back( -17 );
         vecInt.push_back( 3 );
 
         vector<int>::iteratoriterFind = find( vecInt.begin(),vecInt.end(),4 );
         if (iterFind != vecInt.end() )//注意判斷是否已經找到
         {
                   cout<<*iterFind<<"\n";
         }
         iterFind = find_if(vecInt.begin(),vecInt.end(),equal_ ten <int>);
         if (iterFind != vecInt.end() )
         {
                   cout<<*iterFind<<"\n";
         }
         system( "pause");
         return0;
}



摘自 yuanweihuayan的專欄