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Im having some trouble with an Array in C++. See I want to let the user give the program an input in form of a String, and keep doing it until the user is satisfied. My input is working fine but when i want to store the strings in to an array im running in to some problems. I have to define a size for my array apparently? and is there a way to store the input in 2 or 3 different arrays (depending on the input, which i sort with some if-statements) of strings, and the print them out? My code looks something like this now..

string firstarray[10];
string secarray[10];

//The cin stuff here and reading strings from user-input

    if(MyCondition1){ 
for(int x = 0; x<=9;x++){ 
firstarray[x] = name;  
}

  if(MyCondition2){ 
    for(int x = 0; x<=9;x++){ 
    secarray[x] = name;  
    }

Is there a way to skip the 10-limit of an array? could it be like string 

firstarray[];

?

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1  
What is the problem you are trying to solve with multiple arrays? A vector<string> firstArray; gets rid of the size constraint. – Captain Giraffe Feb 28 '12 at 14:40
You do mean std::string, right? I mean, I don't see a using namespace anywhere... – Mr Lister Feb 28 '12 at 14:40
Well he's used string without std:: in the question. – BoBTFish Feb 28 '12 at 14:43
didn't use std::, a bit new to c++ .. – Handsken Feb 28 '12 at 14:45

2 Answers

up vote 8 down vote accepted

You're looking for a std::list. Or better, a std::vector which lets you access elements by their position.

Both of them can be expanded dynamically.

using namespace std;

// looks like this:
vector<string> firstvector;

firstvector.push_back(somestring); // appends somestring to the end of the vector

cout << firstvector[someindex]; // gets the string at position someindex
cout << firstvector.back(); // gets the last element

About your second question:
You can of course create several arrays / vectors to put your strings in. Maybe even use a std::map of type map<key, vector<string>> where key can be an enum for the category (or a string, but enum is better).

You put a new value into one of the vectors:

tCategoryEnum category = eCategoryNone;
switch(condition)
{
  case MyCondition1:
    category = eCategory1;
    break;
  case MyCondition2:
    category = eCategory2;
    break;
  // ...
}
// check if a category was found:
if(category != eCategoryNone)
{
    categoryMap[category].push_back(name);
}

Then to output this, you can simply loop over each category and vector element

for(int i = 0; i < categoryMap.size(); i++)
  for(int j = 0; j < categoryMap[i].size(); j++)
    cout << categoryMap[i][j];
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up vote 5 down vote

Have you considered using an std::vector<string> > ?

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i have encounterd it in some google-result. But i thought that it was to "over do it", guess i was wrong. Can some one link a how-to? – Handsken Feb 28 '12 at 14:44
1  
@Handsken no way is this overdoing it, vectors are simpler to use than arrays. Look at Martin's example it should get you on the right track. – Motti Feb 28 '12 at 14:51

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