left-pad

Your mission

Rebuild left-pad: copy a string into a buffer, padded on the left to a minimum width.

today's brief

March 2016. A developer gets into a naming fight with npm, and in protest he unpublishes all his tiny packages. One of them, left-pad, is eleven lines long. Within minutes Babel, React and thousands of builds around the world fall over at once, every one of them missing the same eleven lines. You are on call the night the internet forgot how to pad a string. Rebuild them.

See it in action

left_pad(dst, "1", 5, '0')

Expected result

[00001]

Your checklist

For your own tracking. Tests grade your code.

Write into dst the string s padded on the left with the fill character.
Pad until dst is at least width characters long.
If s is already width characters or longer, copy it unchanged.
Always null-terminate dst, and do not print anything yourself.
The checker wraps your dst in square brackets so the padding is easy to see.

More examples

left_pad(dst, "foo", 5, ' ')

Expected result

[  foo]

left_pad(dst, "hello", 3, 'x')

Expected result

[hello]

Constraints

Expected files

leftpad.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions

left-pad

Your mission

Rebuild left-pad: copy a string into a buffer, padded on the left to a minimum width.

today's brief

See it in action

left_pad(dst, "1", 5, '0')

Expected result

[00001]

Your checklist

For your own tracking. Tests grade your code.

Write into dst the string s padded on the left with the fill character.
Pad until dst is at least width characters long.
If s is already width characters or longer, copy it unchanged.
Always null-terminate dst, and do not print anything yourself.
The checker wraps your dst in square brackets so the padding is easy to see.

More examples

left_pad(dst, "foo", 5, ' ')

Expected result

[  foo]

left_pad(dst, "hello", 3, 'x')

Expected result

[hello]

Constraints

Expected files

leftpad.c

Allowed functions

None. Write every helper yourself.

Back to compete

Solutions