Question

C++, a simple question.


Can you please tell me how I can create an array that will return a value like this? A[i] = Variable(space)Variable


2 variables is the catch

Answer 1

Well, what are the variables? Is any other method of parring them allowed?

Answer 2

Yes many methods would be welcome. The variables with be Char(space)Int

Answer 3

OK, so they are different data types. Does it have to be in an array, or are you allowed to use a structure?

Answer 4

I am allowed to use structure

Answer 5

Is this for that count the number of letters problem?

I did it an interesting way. See, the ASCII value for 'a' is 97. 'b' us 98 and so on.

So, if I do this:
```
int letter_count[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
// Empty integer array with 26 spots.
```
Now, whenever I detect an a, I do `letter_count[0]++` and for a c it is `letter_count[2]++` and so on.

When I print it out, I just need to print the character based on the iterator plus 97.
```
for(int i = 0 ; i<26 ; i++){
cout << (char)(i+97) << ":" << letter_count[i];
}
```

Answer 6

But how can you erase non zero values ?

Answer 7

sorry I ment *zero values

Answer 8

yes its for that problem

Answer 9

With an if statement.

Answer 10

but if I erase a zero value with an if statement , how can I move the first non zero value from the next line to the last position of the previews line ?

Answer 11

Do you understand what I mean ?

Answer 12

remember 4 non zeros each row

Answer 13

You do not need to. As you cycle through the array, only print and advance a counter for number of items printed inside the if statement. When the counter reaches %4==0 also print an endl. So it will have a nested if statement for that part.

Answer 14

I understand !

Answer 15

That was what the `int newline = 0` in my example the other day was about. =)

Answer 16

ohh I see now

Answer 17

Btw did you understand the other way I was thinking of doing it ? Would it be easy for you to tell me a way of creating an array with 2 separate variables ?

Answer 18

2 seperate variables for each position

Answer 19

of the array

Answer 20

The problem is that an array can only be of one type. Hmmm... but you could cheat that a few different ways. In fact, two arrays would be not hard and at your skill level.

Answer 21

This shows the key to my crafty method:
```
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <cstring>

using namespace std;

int main()
{
int newline = 0;
for (int i = 64 ; i < 127 ; i++)
{
cout << i << ":" << (char)i << " " ;
newline++;
if (newline%10==0) cout << endl;
}

cout << "\n\n";


char test[]="abcxyzABCXYZ";
for (int i = 0 ; i < 12 ; i++)
{
cout << "i=" << i;
cout << " t[" << i << "]=" << test[i];
cout << " (int)t[" << i << "]=" << (int)test[i] << " ";
cout << endl;
}
return 0;
}
```

But that is probably overkill in your case. Yah, 2 arrays using the same iterator is simple!

Answer 22

so with this code you just showed me, you used an array with 2 variables of a different type on each position ?

Answer 23

I do it in one array with that.

But for you, try this:

```
int letter_count[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
char letter_letter[]="abcdefghijklmnopqrstuvwxyz";

letter_count[5]=3

cout << letter_letter[5] << letter_count[5];
```

See what that gets you. I think you can work with it from there.

Answer 24

ok and something last. Would it be possible for me to do it with structure and/or the function strcat() ?

Answer 25

A structure would let you organize things better from a traditional c++ point of view.

```
struct letterCount
{
char letter;
int count;
};
```
Then there is an array of 26 for the alphabet, or 26 individually declared ones... all depends on how you wanted to work with it.

Answer 26

ok and with strcat() ? I have tried using strcat() to solve my problem but to no avail. Maybe it's because of my lack of experience , maybe it's just not even possible ?

Answer 27

That is for copying a string... I don't know what it would be used for in there.

Answer 28

nono for copying it's strcpy() , strcat() is for connecting 2 strings together

Answer 29

Well, it is to copy it onto the tail. That is what I meant. Concatination is what they call it.

Answer 30

for example strcat(p[i],u[i]) p[i] = letter u[i] = count

Answer 31

or strcat(p[i],times)

Answer 32

OH! Well, the count is an integer, not a character.

Answer 33

strcat only works wih strings, not integers.

Answer 34

This? *strcat(&r[i],&times)

Answer 35

I don't even know what it does , my compiler fixed it for me

Answer 36

Pointers. Which compiler?

Answer 37

It's Xcode , I am using mac

Answer 38

So can I use pointers for this thing ?

Answer 39

I don't think it wll work right because it is still incorrect types.

Sort of like the problem with doing `"1"+1` in a computer. The quotes make the first into a string but the second is an integer. They can not be added.

Answer 40

I see man, well thank for very much for taking the time to help me address my problems, I will take some time to use the methods we discussed above in order to find a way to solve it !

Answer 41

Work with the two arrays. That is easist and will work with what you know. And remember, you can reuse an iterator!

```
for(int i = 0 ; i < 5 ; i++){
array_1[i]
array_2[i]
}
```

Answer 42

That code will not run... but it shows how two arrays can be cycled through at the same time.

Answer 43

but what is an iterator ? Also the current lesson is teaching us structures !

Answer 44

Aaaah... if learning structures, then doing it in a structure might be best.

Answer 45

To iterate...
: to say or do again or again and again : reiterate
http://www.merriam-webster.com/dictionary/iterate

In computers, an iterator is the counter in a loop. So as you loop (do it again and again) the iterator keeps track of where you are at the moment.

Answer 46

oh I see !

Answer 47

Yah, they tak a lot from English... then morph it into computer lingo.

Answer 48

Have you learned dot notation for structures?

Answer 49

if you mean things like that: http://screencast.com/t/bmbqwdUoQg Yes but I don't understand it :(

Answer 50

@e.mccormick

Answer 51

Do I need to use this for this problem?

Answer 52

If you want them in a struct, yah.

Answer 53

I see :/

Answer 54

Play with this code some:
```
struct letterCount
{
char letter;
int count;
};

int main()
{
letterCount counter[] = {{'a',0},{'b',0},{'c',0}};

counter[2].count += 2;
counter[2].count++;
counter[0].count += 99;

for (int i=0; i < 3; i++)
{
cout << counter[i].letter << ':' << counter[i].count << endl;
}
```

Answer 55

Note that whan you fill an array of structures that way, ORDER MATTERS! Because my letter is declaied first in the structure, I have to add the character first when I populate the array.