Arrays

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Join Date: Dec 2007

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OmniX

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Arrays

Jul 18th, 2008

I would like to make a "changable" array.

Meaning:
- Not initializing the size.
- Add arrays to the array.
- Remove arrays from the array.

I expect the array size to be 9million or something similar.

Was not sure the best plan of attack after googling and reading books.

Small example if you could please of the 3 points.

Thanks, Regards X.

"You never stop learning" - OmniX

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niek_e

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Re: Arrays

Jul 18th, 2008

The answer would be vectors:

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
#include <iostream>
#include <vector>
using namespace std;
 
int main()
{
   const int maxsize = 9000000;
   vector<int> lst;
   lst.resize(maxsize);
   for(int i = 0; i < maxsize; i++)
       lst[i] = 0;
   return 0;
}
#include <iostream>
#include <vector>
using namespace std;

int main()
{
   const int maxsize = 9000000;
   vector<int> lst;
   lst.resize(maxsize);
   for(int i = 0; i < maxsize; i++)
       lst[i] = 0;
   return 0;
}

To add array's, you could use a vector of vectors, or a map
2d vectors:

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
#include <iostream>
#include <vector>
using namespace std;
 
int main()
{
    const int maxsize = 9000000;
    vector<int> lst;
    lst.resize(maxsize);
    for(int i = 0; i < maxsize; i++)
        lst[i] = 0;
    // 9 million elements in 1 vector
 
    vector< vector <int> > array_vector;
    array_vector.push_back(lst);
    array_vector.push_back(lst);
    // now 2 vectors in array_vector, so 18 millions ints
    return 0;
}
#include <iostream>
#include <vector>
using namespace std;

int main()
{
    const int maxsize = 9000000;
    vector<int> lst;
    lst.resize(maxsize);
    for(int i = 0; i < maxsize; i++)
        lst[i] = 0;
    // 9 million elements in 1 vector

    vector< vector <int> > array_vector;
    array_vector.push_back(lst);
    array_vector.push_back(lst);
    // now 2 vectors in array_vector, so 18 millions ints
    return 0;
}

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OmniX

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Re: Arrays

Jul 18th, 2008

Very nice!

I heard vectors mentioned before (for what it matters I have no idea what vectors are

)
Anyways two questions:
You have initialized the array, for my purposes I cant initialize it. Is this possible?

You have said to add an array but not to remove?

So is it possible to add/remove arrays from a not initialized array?

Sorry about the questions, just new

Thanks, Regards X

PS: I also require a function to break up the array into individual variables, how would I do that? Thanks Again

Last edited by OmniX : Jul 18th, 2008 at 4:37 am.

"You never stop learning" - OmniX

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niek_e

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Re: Arrays

Jul 18th, 2008

•

Originally Posted by OmniX

You have initialized the array, for my purposes I cant initialize it. Is this possible?

You have said to add an array but not to remove?

So is it possible to add/remove arrays from a not initialized array?

PS: I also require a function to break up the array into individual variables, how would I do that? Thanks Again

To answer all your questrions, I've made a small demo with vectors:

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
#include <iostream>
#include <vector>
using namespace std;
 
void show(vector <int> l)
{
    cout << "\n\nIn vector: \n---------------------\n";
    for (unsigned int i  = 0; i < l.size(); i++)
        cout << l[i] << "\n"; //access member in similar way to array's
    cout << "\n---------------------\n";
    cout << "size of vector = " << l.size() << "\nPress enter...";
    cin.get();
}
 
int main()
{
    vector<int> lst;
    lst.push_back(1);  //add number
    show(lst);
    lst.push_back(2222);//add another number
    show(lst);
    lst.pop_back(); //pop the last number
    show(lst);
    return 0;
}
#include <iostream>
#include <vector>
using namespace std;

void show(vector <int> l)
{
    cout << "\n\nIn vector: \n---------------------\n";
    for (unsigned int i  = 0; i < l.size(); i++)
        cout << l[i] << "\n"; //access member in similar way to array's
    cout << "\n---------------------\n";
    cout << "size of vector = " << l.size() << "\nPress enter...";
    cin.get();
}

int main()
{
    vector<int> lst;
    lst.push_back(1);  //add number
    show(lst);
    lst.push_back(2222);//add another number
    show(lst);
    lst.pop_back(); //pop the last number
    show(lst);
    return 0;
}

Last edited by niek_e : Jul 18th, 2008 at 4:51 am.

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OmniX

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Re: Arrays

Jul 18th, 2008

Thanks niek_e, very sexy indeed!!!

I think the only thing left is
"I also require a function to break up the array into individual variables, how would I do that?"

I require:
- 5 variables which are used to make a string
- string is then brokern up into 5 variables
Eg.
input = 1, 2, 3, 4, 5
output = 1 2 3 4 5
further output = 1, 2, 3, 4, 5

Then I can try solve my problem.

Hope that makes sense, Any ideas?

Thankyou Regards, X

"You never stop learning" - OmniX

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Re: Arrays

Jul 18th, 2008

To get individual elements of a vector:

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
#include <iostream>
#include <vector>
using namespace std;
 
int GiveMeNumber(vector <int> iV, int i)
{
    if (i < iV.size() && i >= 0)
        return iV[i];
    else 
        return -1;
}
 
int main()
{
    vector<int> lst;
    int elem, number;
    lst.push_back(1);  //add number
    lst.push_back(2222);//add another number
    lst.push_back(333);//add another number
    lst.push_back(4567);//add another number
 
    cout << "which element do you want?\n";
    cin >> elem;
    number = GiveMeNumber(lst, elem);
    if (number < 0) 
        cout << "element doesn't exist, vector is " << lst.size() << " elements (0-" << lst.size()-1 <<")\n" ;
    else
        cout << "element " << elem << " contains number: " << number;
 
    cin.ignore();
    cin.get();
    return 0;
}
#include <iostream>
#include <vector>
using namespace std;

int GiveMeNumber(vector <int> iV, int i)
{
    if (i < iV.size() && i >= 0)
        return iV[i];
    else 
        return -1;
}

int main()
{
    vector<int> lst;
    int elem, number;
    lst.push_back(1);  //add number
    lst.push_back(2222);//add another number
    lst.push_back(333);//add another number
    lst.push_back(4567);//add another number

    cout << "which element do you want?\n";
    cin >> elem;
    number = GiveMeNumber(lst, elem);
    if (number < 0) 
        cout << "element doesn't exist, vector is " << lst.size() << " elements (0-" << lst.size()-1 <<")\n" ;
    else
        cout << "element " << elem << " contains number: " << number;

    cin.ignore();
    cin.get();
    return 0;
}

To break the string into separate numbers, you could use a stringstream and then use getline (with a delimiter to extract all the number.
In the following example, I assume that all the number are separated with a comma ( ',' ) and nothing more. I'm not going to do all your work for you

example:

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
 
 
int main()
{
    stringstream ss;
    string input  = "1,2,3,4,5";
    string buffer;
    ss << input;
    while (getline(ss,buffer,','))
        cout << buffer << "\n";
    cin.get();
    return 0;
}
#include <iostream>
#include <string>
#include <sstream>
using namespace std;


int main()
{
    stringstream ss;
    string input  = "1,2,3,4,5";
    string buffer;
    ss << input;
    while (getline(ss,buffer,','))
        cout << buffer << "\n";
    cin.get();
    return 0;
}

output:

Help with Code Tags

(Toggle Plain Text)

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OmniX

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Re: Arrays

Jul 18th, 2008

Thanks for all the help niek_e!!!

I totally understand "it is better to teach a person how to fish then to give them a fish"

I will go back and apply the ideas you have mentioned.

Before I go 2 questions:
- You used stringstream to break up the string using a "," if i was using a space it would have just been " ", correct?

- You used buffer to get the broken value from the broken string. Now if I wanted to assign that value to an int I would have used one = buffer then two = buffer, etc, correct?

Thanks again, Regards X

"You never stop learning" - OmniX

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niek_e

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Re: Arrays

Jul 18th, 2008

•

Originally Posted by OmniX

I totally understand "it is better to teach a person how to fish then to give them a fish"

Very good attitude!

•

Originally Posted by OmniX

Before I go 2 questions:
- You used stringstream to break up the string using a "," if i was using a space it would have just been " ", correct?

Almost. It would be ' ' (single quotes, because it's a char)

•

Originally Posted by OmniX

- You used buffer to get the broken value from the broken string. Now if I wanted to assign that value to an int I would have used one = buffer then two = buffer, etc, correct?

Almost. (

) You would have to do some conversion from std::string (or char) to int. But there's plenty of sample code on the net on that subject. Good luck!

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OmniX

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Re: Arrays

Jul 18th, 2008

Ok ill get back to the drawing board and well see what I can come up with, Thanks for all the help on this thread and the other.

Ill keep you posted.

Thankyou Again, Enjoy your weekend

"You never stop learning" - OmniX

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Re: Arrays

#10

Jul 18th, 2008

Ok few errors, ill tackle one at a time:
- Unable to open file <sstream>
- Code may require debugging

 Help with Code Tags 
 cpp Syntax (Toggle Plain Text) 
#include <iomanip>
#include <iostream.h>
#include <fstream.h>
#include <sstream>
#include <string>
#include <vector>
 
string temp;
string stringi;
stringstream ss;
vector<string> arrayi (6);
 
int one = 1, two = 2, three = 3;
int four = 4, five = 5, six = 6;
 
for (int j=0; j<6; j++) {
 if(j==0) {
  stringi.append(one);
  stringi.append(" ");
 }
 if(j==1) {
  stringi.append(two);
  stringi.append(" ");
 }
 if(j==2) {
  stringi.append(three);
  stringi.append(" ");
 }
 if(j==3) {
  stringi.append(four);
  stringi.append(" ");
 }
 if(j==4) {
  stringi.append(five);
  stringi.append(" ");
 }
 if(j==5) {
  stringi.append(six);
 }
}
 
ss << stringi;
for (int i = 0; i < arrayi.size(); i++) {
 getline(ss, temp,' ');
 arrayi[i] = temp;
}
 
if (one = array[i]) {
 cout << "ONE" << endl;
}
// etc
 
#include <iomanip>
#include <iostream.h>
#include <fstream.h>
#include <sstream>
#include <string>
#include <vector>

string temp;
string stringi;
stringstream ss;
vector<string> arrayi (6);

int one = 1, two = 2, three = 3;
int four = 4, five = 5, six = 6;

for (int j=0; j<6; j++) {
 if(j==0) {
  stringi.append(one);
  stringi.append(" ");
 }
 if(j==1) {
  stringi.append(two);
  stringi.append(" ");
 }
 if(j==2) {
  stringi.append(three);
  stringi.append(" ");
 }
 if(j==3) {
  stringi.append(four);
  stringi.append(" ");
 }
 if(j==4) {
  stringi.append(five);
  stringi.append(" ");
 }
 if(j==5) {
  stringi.append(six);
 }
}

ss << stringi;
for (int i = 0; i < arrayi.size(); i++) {
 getline(ss, temp,' ');
 arrayi[i] = temp;
}

if (one = array[i]) {
 cout << "ONE" << endl;
}
// etc