Solved

Question re: iterators...ASAP...please...

Posted on 2004-10-18
5
265 Views
Last Modified: 2013-12-14
Do I need to use iterators when comparing strings within vectors?
I need to compare strings from one vector to strings in another vector.  The size of the vectors are different.
0
Comment
Question by:jewee
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
5 Comments
 
LVL 4

Accepted Solution

by:
pankajtiwary earned 300 total points
ID: 12343037
Hi jewee,

Do not confuse. Iterators are objects to iterate through the elements of a container ( e.g vector ), if you want to iterate through a vector and so *something* you need iterators. Do check this example out.

// Code not tested
#include <iostream>

using namespace std ;

int main() {
    vector v1<string>(2);
    vector v2<string>(4);

    v1.push_back("abc");
    v1.push_back("def");

    v2.push_back("ghi");
    v2.push_back("jkl");
    v2.push_back("abc");
    v2.push_back("def");

    for ( vector<string>::const_iterator it1 = v1.begin(); it1 != v1.end(); it1++) {
        for ( vector<string>::const_iterator it2 = v2.begin(); it2 != v2.end(); it2++) {
            if ( *it1 == *it2 )
                doSomething();
        }
    }
    return 0 ;
}

Hope this helps.

Cheers!
0
 
LVL 86

Assisted Solution

by:jkr
jkr earned 100 total points
ID: 12343424
Ooops, haven't seen that you opened a seperate Q - here's the code again I posted in the last one:

string str = "substring";
vector<string> vs;

for ( vector<string>::iterator i = vs.begin(); i != vs.end(); ++i) {

    if ( -1 != i->find(str)) {

        cout << "Found " << str->c_str() " in in " i->c_str() << endl;
    }
}

If you want to find the exact match, use

if ( *i == str )

like pankajtiwary already suggested.
0
 
LVL 1

Assisted Solution

by:gugario
gugario earned 50 total points
ID: 12343568
There's two ways you can access elements in a vector... one is using the bracket operator, so if you have...

vector<string> a;
vector<string> b;

you could do

if (a[0] == b[1]) cout << "equal";

another is dereferencing an iterator.. so you could have iteractors to the vectors, like

vector<string>::iterator t1 = a.begin();
vector<string>::iterator t2 = b.begin();

if (*t1 == *t2) cout << "equal";

bracket operators, in my opinion, are easier to use.  and part of the reason you would use a vector is so that you could do the direct access with the brackets..

iterators are good i guess if you need to iterate through both vectors completely... but you could still do it with for loops.

hope that helps.

Gustavo
0
 
LVL 9

Expert Comment

by:jhshukla
ID: 12344692
if you like to use bracket operators like Gustavo, vect.size() is the upper bound.
0
 
LVL 17

Assisted Solution

by:rstaveley
rstaveley earned 50 total points
ID: 12348514
There are a lot of nice algorithms you can use that do the iterator work for you.

e.g.
--------8<--------
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

typedef std::vector<std::string> StringVector;

class match {
      const std::string &name;
      const StringVector& cmp;
public:      
      match(const StringVector& cmp,const std::string& name) : cmp(cmp),name(name) {}
      void operator()(const std::string& str) const
      {
            bool found = find(cmp.begin(),cmp.end(),str) != cmp.end();
            std::cout << str << (found?" found ":" not found ") << "in " << name << '\n';
      }
};

int main()
{

      StringVector v1;
      v1.push_back("abc");
      v1.push_back("def");

      StringVector v2;
      v2.push_back("ghi");
      v2.push_back("jkl");
      v2.push_back("abc");
      v2.push_back("def");

      for_each(v2.begin(),v2.end(),match(v1,"v1"));
}
--------8<--------
0

Featured Post

Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Templates For Beginners Or How To Encourage The Compiler To Work For You Introduction This tutorial is targeted at the reader who is, perhaps, familiar with the basics of C++ but would prefer a little slower introduction to the more ad…
How to install Selenium IDE and loops for quick automated testing. Get Selenium IDE from http://seleniumhq.org Go to that link and select download selenium in the right hand columnThat will then direct you to their download page.From that page s…
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

710 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question