Converting int[] to String in C++

Question

I have a string defined as std::string header = "00110033"; now I need the string to hold the byte values of the digits as if its constructed like this

char data_bytes[] = { 0, 0, 1, 1, 0, 0, 3, 3};
std::string header = new std::string(data_bytes, 8).c_str());

I converted the initial string to int array using atoi. Now i'm not sure how to make the string out of it. Let me know if there is any better approach.

syntax of 2nd line isn't correct. Also, what's the intention of the `new` here? — Karl von Moor, Mar 07 '11 at 17:42
Why do you need to do this? What are you going to do if the array contains a value that is not between 0 and 9? — Karl Knechtel, Mar 07 '11 at 18:03
It's inefficient (due to copying) and a memory leak (due to `new` without storing the pointer for a corresponding `delete`) to say `std::string header = (new std::string(data_bytes, 8))->c_str();` (or whatever it is you meant). You can just say `std::string header(data_bytes, 8);` instead. — Jon Purdy, Mar 07 '11 at 18:18

score 3 · Accepted Answer · edited Apr 11 '15 at 15:20

3

you could write a little function

string int_array_to_string(int int_array[], int size_of_array) {
  string returnstring = "";
  for (int temp = 0; temp < size_of_array; temp++)
    returnstring += itoa(int_array[temp]);
  return returnstring;
}

^untested!

a slightly different approach

string int_array_to_string(int int_array[], int size_of_array) {
  ostringstream oss("");
  for (int temp = 0; temp < size_of_array; temp++)
    oss << int_array[temp];
  return oss.str();
}

edited Apr 11 '15 at 15:20

Optimus Prime

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answered Mar 07 '11 at 17:43

ultifinitus

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@ultifinitus atoi converts string to int, while you need to convert int to string. You need to use itoa, which is not standard function, so probably best solution is to convert int to character by adding '0' (see my solution). You also can use lexical cast: `boost::lexical_cast(int_array[temp]);` – UmmaGumma Mar 07 '11 at 18:01
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Use `std::stringstream` instead, it's safer. – RageD Mar 07 '11 at 20:09
Oh good heavens, I'll revamp it, it was a 5 second function geez! =) – ultifinitus Mar 07 '11 at 20:14

Nawaz · Answer 2 · 2011-03-07T18:30:24.473

2

Do this:

  char data_bytes[] = { '0', '0', '1', '1', '0', '0', '3', '3', '\0'};
  std::string header(data_bytes, 8);

Or maybe, you want to do this:

  std::stringstream s;
  s << data_bytes;
  std::string header = s.str();

Demo at ideone : http://ideone.com/RzrYY

EDIT:

Last \0 in data_bytes is necessary. Also see this interesting output here: http://ideone.com/aYtlL

PS: I didn't know this before, thanks to Ashot I came to know this difference by experimenting!

edited Mar 07 '11 at 18:30

answered Mar 07 '11 at 17:44

Nawaz

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You can't store ints in a char array – Nick Rolando Mar 07 '11 at 17:46
@Nawaz -1 data_bytes is not ending with '\0' so you can't print it. + In both cases your string will not be equal to string("00110033"); – UmmaGumma Mar 07 '11 at 17:53
You won't get the results you expect – Nick Rolando Mar 07 '11 at 17:53
@Ashot: I saw that, and fixed it as well. @Nicklamort: The problem is fixed. However, it was nothing to do with "storing ints ina char". – Nawaz Mar 07 '11 at 17:54
@Nawaz remove last '\0' in data_bytes. Your string is ending with double '\0' now :) See this topic http://stackoverflow.com/questions/4711449/what-does-the-0-symbol-mean-in-a-c-string. – UmmaGumma Mar 07 '11 at 18:09
@Ashot: I think that is correct. See this (sizeof vs. strlen): http://ideone.com/aYtlL – Nawaz Mar 07 '11 at 18:14
@Eugen Constantin Dinca you are right, thet's why I undo my downvote, but if last '\0' is not necessary, why write it? – UmmaGumma Mar 07 '11 at 18:16
@Ashot: I updated the link in my previous comment. Please see it again : http://ideone.com/aYtlL – Nawaz Mar 07 '11 at 18:16
@Nawaz, I can't re vote for this answer until you don't edit your question – UmmaGumma Mar 07 '11 at 18:25
Perhaps you should provide an answer matching the question instead of interpreting the question to match your answer. – Eugen Constantin Dinca Mar 07 '11 at 18:25
@Ashot: I not only edited, but also mentioned the difference. Learned something new today. Thanks! – Nawaz Mar 07 '11 at 18:31

score 1 · Answer 3 · answered Mar 07 '11 at 17:46

1

 char data_bytes[] = { 0, 0, 1, 1, 0, 0, 3, 3};
  std::string str;
 for(int i =0;i<sizeof(data_bytes);++i)
      str.push_back('0'+data_bytes[i]);

answered Mar 07 '11 at 17:46

UmmaGumma

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score 1 · Answer 4 · answered Mar 07 '11 at 17:48

1

Assuming you're using a "fairly normal" system where the numeric values of '0' to '9' are consecutive, you can just iterate over each element and subtract '0':

for(int i = 0; i < header.size(); ++i)
{
    header[i] -= '0';
}

answered Mar 07 '11 at 17:48

Mark B

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Shouldn't you be adding instead of substracting? – Eugen Constantin Dinca Mar 07 '11 at 18:23
@Eugen Constantin Dinca The OP has a string like "00111" and wants it to be translated to one with those actual byte values, for example "00111" -> "\000\000\001\001\001". Thus you subtract. – Mark B Mar 07 '11 at 20:16

score 1 · Answer 5 · answered Mar 07 '11 at 17:53

1

You can do this:

std::string header( data_bytes, data_bytes + sizeof( data_bytes ) );
std::transform( header.begin(), header.end(), header.begin(), 
     std::bind1st( std::plus< char >(), '0' ) );

answered Mar 07 '11 at 17:53

Eugen Constantin Dinca

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score 0 · Answer 6 · answered Nov 03 '19 at 08:20

0

If integ[] is the integer array, and s is the final string we wish to obtain,

string s="";

for(auto i=0;i<integ.size()-1; ++i)
    s += to_string(ans[i]); 

cout<<s<<endl;

answered Nov 03 '19 at 08:20

Pe Dro

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Converting int[] to String in C++

6 Answers6

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