v0.40: Create exercises. Challenge the community.

strcat

Your mission

Implement gm_strcat, your own strcat, which appends the src string onto the end of the dst string, then returns dst.

See it in action

gm_strcat("src/", "main.c")

Expected result

src/main.c

Your checklist

For your own tracking. Tests grade your code.

First walk dst to find its \0, that terminator marks where the existing string ends and where the new characters must start.
Copy every character of src to that position, advancing through both buffers.
Write a final \0 after the last copied character so the result is a valid, null-terminated string.
Return the original dst pointer. Assume dst is large enough to hold both strings.
Appending an empty src must leave dst unchanged.

More examples

gm_strcat("rebase done", "")

Expected result

rebase done

Constraints

Expected files

strcat.c

Allowed functions

None. Write every helper yourself.

libc

Standard C library

Implements the contract of a function from the standard C library.

strcat

Writing text without overflowing

Your mission

Implement gm_strcat, your own strcat, which appends the src string onto the end of the dst string, then returns dst.

See it in action

gm_strcat("src/", "main.c")

Expected result

src/main.c

Your checklist

For your own tracking. Tests grade your code.

First walk dst to find its \0, that terminator marks where the existing string ends and where the new characters must start.
Copy every character of src to that position, advancing through both buffers.
Write a final \0 after the last copied character so the result is a valid, null-terminated string.
Return the original dst pointer. Assume dst is large enough to hold both strings.
Appending an empty src must leave dst unchanged.

More examples

gm_strcat("rebase done", "")

Expected result

rebase done

Constraints

Expected files

strcat.c

Allowed functions

None. Write every helper yourself.

libc

Standard C library

Implements the contract of a function from the standard C library.

Tests

Run the tests to grade your code

Build your code, then check each test here. Open a result to inspect its output.

Build

01Append to an empty destinationWaiting

02Append to a non-empty destinationWaiting

03Build a branch nameWaiting

04Append an empty sourceWaiting

05Both strings emptyWaiting

06Build a file pathWaiting

07Result stays NUL-terminated over dirty memoryWaiting

strcat

Your mission

Implement gm_strcat, your own strcat, which appends the src string onto the end of the dst string, then returns dst.

See it in action

gm_strcat("src/", "main.c")

Expected result

src/main.c

Your checklist

For your own tracking. Tests grade your code.

First walk dst to find its \0, that terminator marks where the existing string ends and where the new characters must start.
Copy every character of src to that position, advancing through both buffers.
Write a final \0 after the last copied character so the result is a valid, null-terminated string.
Return the original dst pointer. Assume dst is large enough to hold both strings.
Appending an empty src must leave dst unchanged.

More examples

gm_strcat("rebase done", "")

Expected result

rebase done

Constraints

Expected files

strcat.c

Allowed functions

None. Write every helper yourself.

libc

Standard C library

Implements the contract of a function from the standard C library.

v0.40: Create exercises. Challenge the community.

Meet Studio →

strcat

Writing text without overflowing

Your mission

Implement gm_strcat, your own strcat, which appends the src string onto the end of the dst string, then returns dst.

See it in action

gm_strcat("src/", "main.c")

Expected result

src/main.c

Your checklist

For your own tracking. Tests grade your code.

First walk dst to find its \0, that terminator marks where the existing string ends and where the new characters must start.
Copy every character of src to that position, advancing through both buffers.
Write a final \0 after the last copied character so the result is a valid, null-terminated string.
Return the original dst pointer. Assume dst is large enough to hold both strings.
Appending an empty src must leave dst unchanged.

More examples

gm_strcat("rebase done", "")

Expected result

rebase done

Constraints

Expected files

strcat.c

Allowed functions

None. Write every helper yourself.

libc

Standard C library

Implements the contract of a function from the standard C library.

Tests

Run the tests to grade your code

Build your code, then check each test here. Open a result to inspect its output.

Build

01Append to an empty destinationWaiting

02Append to a non-empty destinationWaiting

03Build a branch nameWaiting

04Append an empty sourceWaiting

05Both strings emptyWaiting

06Build a file pathWaiting

07Result stays NUL-terminated over dirty memoryWaiting