Convert 1 to 01 in C++ without using function

Question

int a;
std::cout<<"Enter hour: ";
std::cin>>a;
std::cout<< a;

This is just for question purpose. Is there any trick to output 01 instead of 1 without using a function? Suppose if the input is 9 I want 09 to be an output but if the 'a' is 2 digit there is no need to add 0.

Either do what @WilliamPursell said, or perhaps use something in `` — Charles, Sep 15 '17 at 03:00
You'll have to describe your problem further. What happens if `a = 10` or `100`, for instance? Is this decimal, binary, hex or what, etc. — Ken Y-N, Sep 15 '17 at 03:01
Dup of [How can I pad an int with leading zeros when using cout << operator?](https://stackoverflow.com/a/1714538/1270789). — Ken Y-N, Sep 15 '17 at 03:10
@KenY-N I asked if it can be done without using any predefined functions. — Bibek, Sep 15 '17 at 03:13
If it's less than 10, print a 0 first. https://ideone.com/ovVT2P — Retired Ninja, Sep 15 '17 at 03:24
No. You are using operator `<<`, which is already a predefined function, which in turn calls a lot of other predefined functions. — , Sep 15 '17 at 05:28
@Bibek -- How far are you going to go with not using "predefined functions"? As pointed out `operator <<` is a predefined function, as well as `operator >>`. It is very rare to find a C++program written just using straight out C++ syntax with no calls (whether implicit or explicit) to library functions. — PaulMcKenzie, Sep 15 '17 at 15:45

score 4 · Accepted Answer · edited Apr 22 '22 at 23:03

4

I think you want:

std::cout << std::setw(2) << std::setfill('0') << a;

This sets the field width to 2 and the fill character to '0'. Keep in mind, however, that although the field width is reset after outputting a, the fill is not. So if this is temporary, be sure to save the fill before setting it.

BTW these function are in "iomanip" library

edited Apr 22 '22 at 23:03

Community

1
1

answered Sep 15 '17 at 03:11

md5i

3,018
1
18
32

Is there any way to do it without using pre-defined functions? – Bibek Sep 15 '17 at 03:14
3

No, as `operator<<` is a pre-defined function. – md5i Sep 15 '17 at 12:30

score 0 · Answer 2 · 2017-09-16T03:41:56.747

0

maybe:

std::cout << ((a <= 9) ? 0 : "") << a;

edited Sep 16 '17 at 03:41

answered Sep 15 '17 at 03:04

score 0 · Answer 3 · answered Sep 15 '17 at 03:17

0

You could use the fine Boost.Format library to format the output with printf-like syntax.

#include <boost/format.hpp>
#include <iostream>

int main()
{
    std::cout << boost::format("%02d") % 1 << '\n';
}

answered Sep 15 '17 at 03:17

Henri Menke

10,705
1
24
42

score 0 · Answer 4 · answered Jan 03 '23 at 14:59

0

You can use:

#include <iomanip>

ans=1;
cout<<setw(2)<<setfill('0')<<ans<<endl;

OUTPUT: 01

answered Jan 03 '23 at 14:59

Yash Raj Mani

51
3

Convert 1 to 01 in C++ without using function

4 Answers4