Solved

C++ Vectors

Posted on 2010-09-01
4
461 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

Highfive + Dolby Voice = No More Audio Complaints!

Poor audio quality is one of the top reasons people don’t use video conferencing. Get the crispest, clearest audio powered by Dolby Voice in every meeting. Highfive and Dolby Voice deliver the best video conferencing and audio experience for every meeting and every room.

Join & Write a Comment

Suggested Solutions

Title # Comments Views Activity
Using YubiKey with REST API application 2 82
mapAB Challlenge 35 89
delphi parse string to params 3 82
Java Loop 4 22
This article will show, step by step, how to integrate R code into a R Sweave document
Whether you've completed a degree in computer sciences or you're a self-taught programmer, writing your first lines of code in the real world is always a challenge. Here are some of the most common pitfalls for new programmers.
In this fourth video of the Xpdf series, we discuss and demonstrate the PDFinfo utility, which retrieves the contents of a PDF's Info Dictionary, as well as some other information, including the page count. We show how to isolate the page count in a…
In this seventh video of the Xpdf series, we discuss and demonstrate the PDFfonts utility, which lists all the fonts used in a PDF file. It does this via a command line interface, making it suitable for use in programs, scripts, batch files — any pl…

760 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

Need Help in Real-Time?

Connect with top rated Experts

19 Experts available now in Live!

Get 1:1 Help Now