Thread: append character to array

Quick question all, how do you append a character to an array? Say for example I prompt the user for a string and store that value in a array.
later on, I accept another value(a key) and store that value in a array.
I want the length of the first array to equal to the length of the key.

For example:

daryl--plaintext
Kyle Peterson-Key value

I want (daryl) to repeat until it equals the length of Kyle Peterson.But I want to append it to an existing array. How do I do that? suggestions would be appreciated. Thanks!

Originally Posted by laserlight

What ideas do you have in mind?

In other words, where is my code?

The code I have looks like this:

Code:

a=e //where e is the length of plain text string
m=//length of key string
for int i=a;i<m, i++)

{
    plaintext[a] =plaintext[i];
}

Originally Posted by laserlight

Not really: ideas and code aren't exactly the same thing. I'm asking you to describe some idea that you have to solve this, perhaps outline an algorithm.

I see, but the code I have would not work?

I have an idea of what to do now. I see my problem. if I did this:

Code:

=e //where e is the length of plain text string m=//length of key string
tempvalue  =m-e
 
for int i=0;i<tempvalue, i++) 

{ 
plaintext[e] =plaintext[i]; 
}

That would allow me to to repeat the character at the location i after the location e in plaintext array. Correct?

If you can guarantee that the arrays are big enough to fit the key string then you might not need to do dynamic allocation. It depends -- the "size" of the array will be the size it was declared with, but the string length can vary independently.

Code:

=e //where e is the length of plain text string m=//length of key string
tempvalue  =m-e
 
for int i=0;i<tempvalue, i++) 

{ 
plaintext[e] =plaintext[i]; 
}

I think I can see what you're trying to do, maybe. If you recalculate the length of plaintext each time through the loop, it'll work. However it'll only work if you have a reliable way of working out the length of the string. strlen() counts the characters up until the NULL terminator, which you'll overwrite with your copy code.

So you could:

Code:

for (int i=0;i<tempvalue, i++) 
{ 
    e = strlen(plaintext);
    plaintext[e] =plaintext[i]; 
    plaintext[e+1] = 0;
}

That's not a very efficient way of doing it though -- calling strlen every time through the loop. It's not necessary.

Say your plaintext is "hello". Then you want to copy element 0 to element len(hello), element 1 to len(hello)+1, element 2 to len(hello)+2 and so on. The difference between where you copy from and to is always the same: it's the original length of plaintext.

Don't forget that you'll still need to NULL terminate the new plaintext.