argsort_len

Pointers24

Objective

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

Steps

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.

examples

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

1 0 2

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

1 2 0

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

1 0 2 vim ed emacs

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

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

01Three distinct lengths

02Length decides before bytes do

03Equal lengths broken by bytes

04Uppercase bytes sort before lowercase

05Equal strings keep index order

06n of zero writes nothing

07Single string

08Input already ordered by length

09Input in exactly reverse order

10Empty string comes first

11Two empty strings and two singles

12Two groups of equal length

13Reads n entries and writes n values

14arr is not reordered

15Several groups, ties and an empty string

argsort_len

Objective

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

Steps

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.

examples

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

1 0 2

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

1 2 0

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

1 0 2 vim ed emacs

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

99 99

Constraints

Expected files

argsort_len.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

argsort_len

Pointers24

Objective

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

Steps

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.

examples

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

1 0 2

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

1 2 0

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

1 0 2 vim ed emacs

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

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

01Three distinct lengths

02Length decides before bytes do

03Equal lengths broken by bytes

04Uppercase bytes sort before lowercase

05Equal strings keep index order

06n of zero writes nothing

07Single string

08Input already ordered by length

09Input in exactly reverse order

10Empty string comes first

11Two empty strings and two singles

12Two groups of equal length

13Reads n entries and writes n values

14arr is not reordered

15Several groups, ties and an empty string