Re: Searching in sorted containers

From:
"Greg Herlihy" <greghe@pacbell.net>
Newsgroups:
comp.lang.c++.moderated
Date:
14 Jun 2006 13:01:50 -0400
Message-ID:
<1150089332.720138.58610@h76g2000cwa.googlegroups.com>
????????????????????? ?????????????????????????????????????? wrote:

Hello all,

suppose we have the following class:

class A {
public:
   const string& getName() const;

   bool operator<(const A& rhs) const {
     return getName() < rhs.getName();
   }

   /* more fields and methods here */
};

and that we have a container sorted on the value of the getName() method.

How can one search for the item with a given value of the getName()
method knowing that algorithms like std::lower_bound wouldn't accept a
string as a search item?

I need to write something like:

std::vector<A> v;
/* Fill v */
std::sort(v.begin(), v.end());
std::lower_bound(v.begin(), v.end(), /* want to put a string here */));


The easiest solution would be to overload the < (less than) operator
with a std::string and a class A object as its operands:

     bool operator<(const A& lhs, const std::string& rhs)
     {
         return lhs.getName() < rhs;
     }

     bool operator<(const std::string& lhs, const A& rhs)
     {
         return lhs < rhs.getName();
     }

     int main()
     {
         std::vector<A> v;
         /* Fill v */
         std::sort(v.begin(), v.end());

         // "search" converts to a std::string...
         std::lower_bound(v.begin(), v.end(), "search");
     }

Greg

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