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
Solved

C++ Vectors

Posted on 2010-09-01
4
492 Views
Last Modified: 2012-05-10
I was looking at figuring out what the quickest way of 'finding' a value in vectors are.

For example, when I scan through all my ships in game, I'll do something like:

      const ShipClass *ship = &game->ship[0];
      const ShipClass* end1 = ship + Nobj;
      while (ship != end1)
      {
            if (ship && ship->active) {
                                      //DO STUFF HERE
            }
            ship++;
      }

I'm wondering to 'find', I need to do something similar, going through an array and matching it with what I'm looking for, like:

              int findthis = 30;
      const ShipClass *ship = &game->ship[0];
      const ShipClass* end1 = ship + Nobj;
      while (ship != end1)
      {
            if (ship && ship->id == findthis) {
                                      //DO STUFF HERE
            }
            ship++;
      }


Rather, I am wondering if this is the fastest possible solution for this, or if there is a better/quicker method for finding a value in a vector list.

Any suggestions/tips? Thanks!
0
Comment
Question by:Valleriani
  • 2
4 Comments
 
LVL 40

Accepted Solution

by:
evilrix earned 250 total points
ID: 33581603
0
 
LVL 12

Expert Comment

by:w00te
ID: 33581865
This is from memory, but it should work for a simple function.  It's an example of the kind of things evilrix is pointing out.
It uses a template function though, you just pass in the int value you want to search for as a template parameter and it looks for it.  You could adjust this to take in any value (including another Ship object), and you can perform whatever comparisons you want in the function.  Find if will always give the iterator to the first position the said value was found in.
Most of the code is just there to set up the vector, the find if function accomplishes pretty much everything :)
Enjoy,
(PS, I compiled it on linux but i had to type it on windows where there istn a compiler, so if theres a typo just try and fix it, the idea works ;) )
-w00te

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct Ship
{
	int id;
	Ship(int x) : id(x) {}
};

int main()
{
	template <int T>
	bool FindCondition(const Ship& ship) {return ship.id == T; }

	vector<Ship> sVec;
	sVec.push_back(Ship(12));
	sVec.push_back(Ship(15));

	vector<Ship>::iterator iter = find_if(sVec.begin(), sVec.end(), FindCondition<15>);

	if (iter != sVec.end())
		cout<<iter->id<<" was found." <<endl;
}

Open in new window

0
 
LVL 12

Assisted Solution

by:w00te
w00te earned 250 total points
ID: 33582179
Sorry about that, tried to compile now, i pushed the template in main accidentally hehe.  Here's the working code:
 template <int T>
 bool FindCondition(const Ship& ship) {return ship.id == T; }

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct Ship
{
	int id;
	Ship(int x) : id(x) {}
};

template <int T>
bool FindCondition(const Ship& ship) {return ship.id == T; }

int main()
{
	vector<Ship> sVec;
	sVec.push_back(Ship(12));
	sVec.push_back(Ship(15));

	vector<Ship>::iterator iter = find_if(sVec.begin(), sVec.end(), FindCondition<15>);

	if (iter != sVec.end())
		cout<<iter->id<<" was found." <<endl;
}

Open in new window

0
 
LVL 7

Author Closing Comment

by:Valleriani
ID: 33584030
Thank you both!
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

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

Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
Although it can be difficult to imagine, someday your child will have a career of his or her own. He or she will likely start a family, buy a home and start having their own children. So, while being a kid is still extremely important, it’s also …
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…
The viewer will learn how to use the return statement in functions in C++. The video will also teach the user how to pass data to a function and have the function return data back for further processing.

840 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