converting an array of integers to string

Question

If I have an array that looks like

int digits[size] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 0, 4}

I want to remove the leading zeros and to do so I'm attempting to convert the array of integers into a string (which is an array of chars).

My attempt looks like

string toString(int digits[], int size){
string number = " ";
for(int i = 0; i < size - 1; i++){
    number[i] = digits[i];
}
return number;
}

which came out horribly broken.

I also can't simply remove all zeros, just the leading ones.

Also if I may dogpile another question here:

how can I identify if a string is numeric?

e.g

string number = "12a4"
cout << "not a number"

Start by looking at this: http://stackoverflow.com/questions/5590381/easiest-way-to-convert-int-to-string-in-c It should help you convert int to string — FCo, Apr 13 '17 at 19:30
Take a look at, https://stackoverflow.com/questions/5223066/converting-int-to-string-in-c — Felipe Lopez, Apr 13 '17 at 19:33
edited my answer to match all your request. Comment my post if you have more issues — RomMer, Apr 13 '17 at 19:42

RomMer · Accepted Answer · 2017-04-13T19:40:39.023

you can use C++11 function std::to_string() here is an example

#include <string>
#include <iostream>

int main()
{
   int size = 15;
   int digits[size] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 0, 4};
   std::string result = "";

   for (int i = 0; i < size; i++)
   {
      if (!(digits[i] == 0 && result.size() == 0))
         result += std::to_string(digits[i]);
   }

   std::cout << result << std::endl;
}

you can check if a string is numeric using this function

bool isNb(std::string str)
{
  if (str.size() == 0)
    return false;

  for (int i = 0; i < str.size(); i++)
  {
    if (std::isdigit(str.at(i)) == false)
      return false;
  }

  return true;
}

score 1 · Answer 2 · answered Apr 13 '17 at 19:35

Instead of changing digits with your for loop, add them with

 number += to_string(digits[i]);

Also, you can remove the toString line you have, and just use it as I put here.

As to your other question, just use a for loop to check each digit in the string and its ASCII value, if there is any whose ASCII value is less than 48 or greater than 57 then it's not a number.

score 1 · Answer 3 · answered Apr 13 '17 at 19:40

1

Try the following way:

int i = 0;
while(digits[i] == 0) i++;
for (; i < size; i++)
   result += to_string(digits[i]);

answered Apr 13 '17 at 19:40

VHS

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3
19
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463035818_is_not_an_ai · Answer 4 · 2017-04-13T19:48:25.547

1

To answer your actual question (How to remove the leading zeros?) here a solution without strings:

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    std::vector<int> x = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 0, 4};
    // ...or if you insist on the array...
    // int x[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 0, 4};
    // std::vector<int> x = {x,x+15};
    auto it = std::find_if_not(x.begin(),x.end(),[](int i){return i==0;});
    std::vector<int> y{it,x.end()};
    for (auto i : y) std::cout << i << " ";
}

prints:

1 2 3 0 4

edited Apr 13 '17 at 19:48

answered Apr 13 '17 at 19:43

463035818_is_not_an_ai

109,796
11
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185

that's a bad practise and he wants to use an array of integers; not a vector – RomMer Apr 13 '17 at 19:44
@RomMer what is bad practice about that? Do you really rather convert an array of integers to a string than to a vector of ints? – 463035818_is_not_an_ai Apr 13 '17 at 19:46
i use vectors; but op didn't if you read his post he uses an array of integer – RomMer Apr 13 '17 at 19:49
@RomMer a vector is just an array (plus a nicer interface) – 463035818_is_not_an_ai Apr 13 '17 at 19:49
@RomMer anyhow, I added some comments in the code so it can be used starting from an array – 463035818_is_not_an_ai Apr 13 '17 at 19:50
https://www.quora.com/What-is-the-difference-between-an-array-and-a-vector – RomMer Apr 13 '17 at 19:51
@RomMer I know that they are not exaclty the same. Sorry for being sloppy... however the post in your link seems to be even more sloppy (if not nonsense). For example "Vector is an abstraction, so you do not know where exactly your data is" thats just not true for a `std::vector` where you know quite well where your data is – 463035818_is_not_an_ai Apr 13 '17 at 19:58

Kostas · Answer 5 · 2017-04-14T03:36:50.977

You can use a string stream to convert from any type to string:

#include <sstream> //<-- ALLOWS USE OF std::stringstream 
const int size = 15;

int digits[size] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 0, 4};

std::stringstream ss;  //<-- DECLARE STREAM

int k;
for (k = 0; k < size; ++k)
        if (digits[k] != 0)
                break; //FIND FIRST NON-0 INDEX

for (int i = k; i < size; ++i)
                ss << digits[i]; //ADD TO THE STREAM s

std::cout<< ss.str() << std::endl; //PRINT STREAM

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converting an array of integers to string

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