v0.40: Create exercises. Challenge the community.

argsort_len

Your mission

Implement a function that fills out with the indices of arr ordered by string length, shortest first, without touching arr itself.

See it in action

char *arr[] = {"gcc", "a", "make"}; argsort_len(arr, 3, out);

Expected result

1 0 2

Your checklist

For your own tracking. Tests grade your code.

arr holds n pointers to NUL terminated strings. Read exactly n of them, never more.
out points to a buffer with room for n values of type size_t. Write the indices 0 to n - 1 there, ordered by the length of the string they point to, shortest first. The examples print out as its values separated by single spaces.
Two strings of the same length are ordered by their bytes: walk them from the start, and the first position where they differ decides, smaller byte value first. Two strings that are equal keep their original relative order, so the lower index comes first.
arr must come out of the call exactly as it went in. Sort the indices, not the pointers, and never write through a pointer either.
Every index from 0 to n - 1 appears in out once and only once. Write exactly n values, nothing past out[n - 1].
When n is 0, leave out completely alone.
You cannot call anything, so write your own length measurement and your own byte comparison.

More examples

char *arr[] = {"zsh", "ash", "csh"}; argsort_len(arr, 3, out);

Expected result

1 2 0

char *arr[] = {"vim", "ed", "emacs"}; argsort_len(arr, 3, out); print out, then arr

Expected result

1 0 2
vim ed emacs

size_t out[2] = {99, 99}; argsort_len(arr, 0, out);

Expected result

99 99

Constraints

Expected files

argsort_len.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

argsort_len

Pointers

Your mission

Implement a function that fills out with the indices of arr ordered by string length, shortest first, without touching arr itself.

See it in action

char *arr[] = {"gcc", "a", "make"}; argsort_len(arr, 3, out);

Expected result

1 0 2

Your checklist

For your own tracking. Tests grade your code.

arr holds n pointers to NUL terminated strings. Read exactly n of them, never more.
out points to a buffer with room for n values of type size_t. Write the indices 0 to n - 1 there, ordered by the length of the string they point to, shortest first. The examples print out as its values separated by single spaces.
Two strings of the same length are ordered by their bytes: walk them from the start, and the first position where they differ decides, smaller byte value first. Two strings that are equal keep their original relative order, so the lower index comes first.
arr must come out of the call exactly as it went in. Sort the indices, not the pointers, and never write through a pointer either.
Every index from 0 to n - 1 appears in out once and only once. Write exactly n values, nothing past out[n - 1].
When n is 0, leave out completely alone.
You cannot call anything, so write your own length measurement and your own byte comparison.

More examples

char *arr[] = {"zsh", "ash", "csh"}; argsort_len(arr, 3, out);

Expected result

1 2 0

char *arr[] = {"vim", "ed", "emacs"}; argsort_len(arr, 3, out); print out, then arr

Expected result

1 0 2
vim ed emacs

size_t out[2] = {99, 99}; argsort_len(arr, 0, out);

Expected result

99 99

Constraints

Expected files

argsort_len.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

Tests

Run the tests to grade your code

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

Build

01Three distinct lengthsWaiting

02Length decides before bytes doWaiting

03Equal lengths broken by bytesWaiting

04Uppercase bytes sort before lowercaseWaiting

05Equal strings keep index orderWaiting

06n of zero writes nothingWaiting

07Single stringWaiting

08Input already ordered by lengthWaiting

09Input in exactly reverse orderWaiting

10Empty string comes firstWaiting

11Two empty strings and two singlesWaiting

12Two groups of equal lengthWaiting

13Reads n entries and writes n valuesWaiting

14arr is not reorderedWaiting

15Several groups, ties and an empty stringWaiting

argsort_len

Your mission

Implement a function that fills out with the indices of arr ordered by string length, shortest first, without touching arr itself.

See it in action

char *arr[] = {"gcc", "a", "make"}; argsort_len(arr, 3, out);

Expected result

1 0 2

Your checklist

For your own tracking. Tests grade your code.

arr holds n pointers to NUL terminated strings. Read exactly n of them, never more.
out points to a buffer with room for n values of type size_t. Write the indices 0 to n - 1 there, ordered by the length of the string they point to, shortest first. The examples print out as its values separated by single spaces.
Two strings of the same length are ordered by their bytes: walk them from the start, and the first position where they differ decides, smaller byte value first. Two strings that are equal keep their original relative order, so the lower index comes first.
arr must come out of the call exactly as it went in. Sort the indices, not the pointers, and never write through a pointer either.
Every index from 0 to n - 1 appears in out once and only once. Write exactly n values, nothing past out[n - 1].
When n is 0, leave out completely alone.
You cannot call anything, so write your own length measurement and your own byte comparison.

More examples

char *arr[] = {"zsh", "ash", "csh"}; argsort_len(arr, 3, out);

Expected result

1 2 0

char *arr[] = {"vim", "ed", "emacs"}; argsort_len(arr, 3, out); print out, then arr

Expected result

1 0 2
vim ed emacs

size_t out[2] = {99, 99}; argsort_len(arr, 0, out);

Expected result

99 99

Constraints

Expected files

argsort_len.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

v0.40: Create exercises. Challenge the community.

Meet Studio →

argsort_len

Pointers

Your mission

Implement a function that fills out with the indices of arr ordered by string length, shortest first, without touching arr itself.

See it in action

char *arr[] = {"gcc", "a", "make"}; argsort_len(arr, 3, out);

Expected result

1 0 2

Your checklist

For your own tracking. Tests grade your code.

arr holds n pointers to NUL terminated strings. Read exactly n of them, never more.
out points to a buffer with room for n values of type size_t. Write the indices 0 to n - 1 there, ordered by the length of the string they point to, shortest first. The examples print out as its values separated by single spaces.
Two strings of the same length are ordered by their bytes: walk them from the start, and the first position where they differ decides, smaller byte value first. Two strings that are equal keep their original relative order, so the lower index comes first.
arr must come out of the call exactly as it went in. Sort the indices, not the pointers, and never write through a pointer either.
Every index from 0 to n - 1 appears in out once and only once. Write exactly n values, nothing past out[n - 1].
When n is 0, leave out completely alone.
You cannot call anything, so write your own length measurement and your own byte comparison.

More examples

char *arr[] = {"zsh", "ash", "csh"}; argsort_len(arr, 3, out);

Expected result

1 2 0

char *arr[] = {"vim", "ed", "emacs"}; argsort_len(arr, 3, out); print out, then arr

Expected result

1 0 2
vim ed emacs

size_t out[2] = {99, 99}; argsort_len(arr, 0, out);

Expected result

99 99

Constraints

Expected files

argsort_len.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

Tests

Run the tests to grade your code

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

Build

01Three distinct lengthsWaiting

02Length decides before bytes doWaiting

03Equal lengths broken by bytesWaiting

04Uppercase bytes sort before lowercaseWaiting

05Equal strings keep index orderWaiting

06n of zero writes nothingWaiting

07Single stringWaiting

08Input already ordered by lengthWaiting

09Input in exactly reverse orderWaiting

10Empty string comes firstWaiting

11Two empty strings and two singlesWaiting

12Two groups of equal lengthWaiting

13Reads n entries and writes n valuesWaiting

14arr is not reorderedWaiting

15Several groups, ties and an empty stringWaiting