c++ converting int to char + add leading zeros to char

Question

I got numbers from 0 to 999. How can I achieve the following

int i = 123;//possible values 0-999
char i_char[3] = /*do conversion of int i to char and add 3 leading zeros*/

Example(s): i_char shall look like "001" for i=1, "011" for i=11 or "101" for i=101

Your array needs to be of size 4, since any sequence of `char`s in C is always terminated by a null char `\0` — Jan Henke, Jul 19 '16 at 14:59

score 5 · Answer 1 · edited Jul 19 '16 at 17:53

5

Use a std::ostringstream with std::setfill() and std::setw(), eg:

#include <string>
#include <sstream>
#include <iomanip>

int i = ...;
std::ostringstream oss;
oss << std::setfill('0') << std::setw(3) << i;
std::string s = oss.str();

edited Jul 19 '16 at 17:53

Remy Lebeau

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answered Jul 19 '16 at 14:57

Cheers and hth. - Alf

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This is more like a hint or a comment than being an answer – Khalil Khalaf Jul 19 '16 at 14:58
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@FirstStep: Read up on "give the man a fish". Please don't vote out of ignorance, as you did now. – Cheers and hth. - Alf Jul 19 '16 at 15:01

score 2 · Accepted Answer · answered Jul 19 '16 at 15:01

2

It appears you are looking for sprintf, or perhaps printf.

int i = 123;
char str[10];
sprintf(str, "%03d", i);

answered Jul 19 '16 at 15:01

Sven Nilsson

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**−1** Using type unsafe `sprintf` is very ungood advice to a newbie. Ditto for the use of a raw array. – Cheers and hth. - Alf Jul 19 '16 at 15:02
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if you recommend this at least recommend `snprintf` – Slava Jul 19 '16 at 15:02

DimChtz · Answer 3 · 2016-07-19T15:11:28.577

0

Since, you tagged the question with c++ here is a quick solution using std::string and std::to_string:

#include <iostream>
#include <string>

int main() {
   int i = 1;
   std::string s = std::to_string(i);

   if ( s.size() < 3 )
       s = std::string(3 - s.size(), '0') + s;

   std::cout << s << std::endl;

   return 0;
}

For i=1 it will output: 001.

edited Jul 19 '16 at 15:11

answered Jul 19 '16 at 15:05

DimChtz

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Please test with `int i = 12345`. Surprise? – Cheers and hth. - Alf Jul 19 '16 at 15:05
Well, he can check if `s.size() < 3`. Let me edit it. – DimChtz Jul 19 '16 at 15:06

c++ converting int to char + add leading zeros to char

3 Answers3