Two Hard-coded Arrays into One 2-Dimensional Vector

[codechick]

Two Hard-coded Arrays into One 2-Dimensional Vector
Hello, I have been working on this issue for a long time, and I need your expertise.
I have 2 arrays, each of them are hard-coded with integer values.
I also have one 2-Dimensional vector and I want to put 1 array into the first column of the vector and the other array into the 2nd column of the vector. The reason is that I want to do math on the 2nd column of the vector only.

I am able to accomplish this with 3 arrays. Two of them are 1-Dimensional and the third array is 2-Dimensional.

I know how to pass ONE Array into ONE vector:

Code:

vector<int> myVector(typeArray, typeArray + 4);

however, when I declare a 2-Dimensional vector:

Code:

vector< vector <int> > myVector(3, vector<int> (2,0))

I am not seeing how to add TWO arrays or how to OUTPUT it to the screen.
Here is my code using DevCPP:

Code:

Code:
#include <iostream>    
#include <vector>
#include <Windows.h>
#include <algorithm>
 
using namespace std;
 
int main()            
{    
 
    int typeArray[3] = {55,66,77};
    int valArray[3] = {1,2,3};
 
    // for vector: 3 = LENGTH or NUMBER of ROWS; 2 = WIDTH or NUMBER of COLUMNS;
    //  0 = VALUE all cells are initialized to
    vector< vector <int> > myVector(3, vector<int> (2,0));
 
     for (int i = 0; i < sizeof(typeArray); i++)
         {
          for (int j = 0; j < sizeof(valArray); j++)
             {
             myVector[i][j];
             }
       // This "cout" statement doesn't work
       //cout << "Vector is now: " << myVector[i][j] << endl;    
         }
 
    system("Pause");
    return 0; 
}
 

I don't get any errors, however, I don't know how to output it to the screen to see what it looks like. Please advise, thanks!

[Banfa]

Line 26 is fine, as long as it is inside the inner loop not outside it were it currently is.

The issue with your code is the loop control conditions e.g. i < sizeof(typeArray). These have nothing to do with the data being accessed which is a little silly because a vector knows how many entries it holds, this one should be i < myVector.size(); and the inner loop should use j < myVector[i].size();.

To initialise you vector you can make use of the vector::assign method.

[codechick]

Hi Banfa,

I apologize for a late response, I posted a reply about your putting the element before the dot operator, however, it doesn't seem to have taken....so, thank you for that information, I was not aware of that method.
To me, what it means is that the "pointer" of the loop with "j" should move to the second element in the vector up to the length of the entire vector, correct?
----------------------------------
I have been working on the code, and I have it corrected.
However, I have a new dimension to the program that I would appreciate your input on:
This is updated code from first post:

    // Example using "sizeof" for loop maximum if arrays are the same size
    for (int i = 0; i < sizeof(typeArray)/sizeof(typeArray[0]); i++)
      {
         myVector[i][0] = typeArray[i];
         myVector[i][1] = valArray[i];
       }
       // print vector to screen
       for (int i = 0; i < myVector.size(); i++)
          {         
            for (int j = 0; j < myVector[i].size(); j++)
             { 
              cout << myVector[i][j] << ' ';
              }         
              cout << '\n';
          }
 

OUTPUT for First Code Submission:
55 1
66 2
77 3
------------------------------
Now, I am using 2 ARRAYS OF DIFFERENT SIZES in One 2-Dimensional Vector, and my output is not correct. I am looking for each row of columns AFTER the 55, 66, 77, 88 to be populated with each number of "valArray."
-----------------
Here is the code and output:

 int typeArray[4] = {55,66,77,88};
    int valArray[13] = {1,2,3,4,5,6,7,8,9,10,10,10,11};
 
    // 4 = LENGTH or NUMBER of ROWS; 13 = WIDTH or NUMBER of COLUMNS;
    //  0 = VALUE all cells are initialized to
     vector< vector <int> > myVector(4, vector<int> (13,0));
 
      for (int i = 0; i < myVector.size(); i++) 
        {
            myVector[i][0] = typeArray[i];
        for (int j = 0; j < myVector[i].size(); j++) 
          {
             myVector[1][j] = valArray[j];
          }
       }
     // print vector to screen with 4 ROWS, 13 COLUMNS
        for (int i = 0; i < myVector.size();  i++)
          {         
            for (int j = 0; j < myVector[i].size(); j++)
             { 
              cout << myVector[i][j] << ' ';
              }         
              cout << '\n';
          }
 

OUTPUT for Second Code Submission:
55 0 0 0 0 0 0 0 0 0 0 0 0
1 2 3 4 5 6 7 8 9 10 10 10 11
77 0 0 0 0 0 0 0 0 0 0 0 0
88 0 0 0 0 0 0 0 0 0 0 0 0
--------------------------------

[Banfa]

Basically this all comes down to how you initialise myVector.

Before you were initialising everything to the same size so vector< vector <int> > myVector(4, vector<int> (13,0)); was working because that is exactly what it does, initialise everything to the same size.

Now you want things to be different sizes (maybe).

I am not convinced at this time that you are using the correct format for your data, before you jump into creating an array to hold your data you should be asking what data do I want to hold for 1 thing in my array. Then if required you create a class (or struct) to hold that data and then you create an array of the class (or struct).

It appears from what you have posted as if you want a data type that contains a type variable with an array of values for the type. A couple of ways you could implement this are

// Option 1: data is contained in the class
class MyThing
{
public:
// Class constructors and data accessors
 
private:
    int type;
    vector<int> data;
};
 

// Option 2: class subclasses vector to hold the data providing a vector with an additional type
class MyThing: public vector<int> data;
{
public:
// Class constructors to allow calling of the vector class constructors
// Data accessors to access type
 
private:
    int type;
};
 

Then in your code you just create a vector of MyThing, remeber with vectors you can reserve capacity without actually using it immediately and then push data into the vector as required

// PSEUDO CODE
std::vector<MyThing> myVector;
 
myVector.reserve(4); // Reserve space for 4 my things
 
// Could be done as a loop if you have an array of types
myVector.push_back(MyThing(55, <DataForType55Thing>));
myVector.push_back(MyThing(66, <DataForType66Thing>));
myVector.push_back(MyThing(77, <DataForType77Thing>));
myVector.push_back(MyThing(88, <DataForType88Thing>));
 

The output of the current code shows very clearly the square nature of the data you have allocated which is a result of the way you declared myVector at line 6 as a vector of 4 vectors of 13 ints. If you want something less square you will need more lines of code. Declare a vector of 4 vectors but size those internal vectors later.

You get 66 in your output because the inner initialisation loop overwrites the data where the 66 is held.

[codechick]

Hello Banfa! Again, my response is late as I'm not sure how to be notified when I have a response? I'd like to get notified by email. I have checked into this site many times and I finally looked deeper and found your answer from 2 weeks ago. I will look into how to get notifications. However, if you know that would be really helpful....anyway, I need to look over your answer in detail, and then I will respond. Next time, it will be right away, thank you again!

[Banfa]

To automatically subscribe to threads you start/reply to then

1. Select "Edit Profile" from the menu at the top of the screen
2. Select "Edit Options" from the meu display of the right hand side of the screen
3. look for "Default Thread Subscription Mode" which is just off the bottom of the screen for me and select the option you want.

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