Here is a simple lib to do some common array operations.
Since cairo is memory immutable (once you write the value in a memory cell, this cell cannot change anymore), each function requiring any memory change, will create a new array. So you can see each function as a copy function with some more extra logic.

This library is divided multiple parts. Here is everything you can do:

Array manipulation

These functions will always have to create a new array to be returned.
All these functions are returning the same values
(arr_len : felt, arr : felt*):

Function	Arguments
add_first	(arr_len : felt, arr : felt*, item : felt)
add_last	(arr_len : felt, arr : felt*, item : felt)
add_at	(arr_len : felt, arr : felt*, index : felt, item : felt)
remove_first	(arr_len : felt, arr : felt*)
remove_last	(arr_len : felt, arr : felt*)
remove_at	(arr_len : felt, arr : felt*, index : felt)
remove_first_occurence_of	(arr_len : felt, arr : felt*, item : felt)
remove_last_occurence_of	(arr_len : felt, arr : felt*, item : felt)
remove_all_occurences_of	(arr_len : felt, arr : felt*, item : felt)
sort	(arr_len : felt, arr : felt*)
reverse	(arr_len : felt, arr : felt*)
join	(arr1_len : felt, arr1 : felt, arr2_len : felt, arr2 : felt)
copy_from_to	(arr_len : felt, arr : felt*, from_index : felt, to_index : felt)
replace	(arr_len : felt, arr : felt*, old_item : felt, new_item : felt)

Array searching

These are all the functions that will iterate through the array and return what is asked.

Function	Arguments	Return
contains	(arr_len : felt, arr : felt*, item : felt)	(contains : felt)
index_of	(arr_len : felt, arr : felt*, item : felt)	(index : felt)
min	(arr_len : felt, arr : felt*)	(min : felt)
index_of_min	(arr_len : felt, arr : felt*)	(index : felt)
max	(arr_len : felt, arr : felt*)	(max : felt)
index_of_max	(arr_len : felt, arr : felt*)	(index : felt)
occurrences_of	(arr_len : felt, arr : felt*, item : felt)	(occurrences : felt)

Tests

Prerequisite - Have a working cairo environment.
To run the test suite, copy this repository and put yourself at the root.
Compile the contracts using make build or nile compile.
Run the tests using make test or, for more details, pytest -v.
For more details check the Actions tab of this GitHub repository.

TODO

Flatten?
Support of structure in a generic way?

Don't hesitate to request me any feature that could be missing or ping me whenever there is the support for returning structure (with felt*)

Detailed description

Array manipulation functions

add_first(arr_len : felt, arr : felt*, item : felt) -> (arr_len : felt, arr : felt*)

Creates a new array with the item at the first position.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
item - the felt that needs to be added

Returns:
arr_len - the length of the new array
arr - the new array

Complexity:
O(N)

add_last(arr_len : felt, arr : felt*, item : felt) -> (arr_len : felt, arr : felt*)

Creates a new array with the item at the last position.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
item - the felt that needs to be added

Returns:
arr_len - the length of the new array
arr - the new array

Remark:
If you still have access to the array, and the memory isn't bounded already, consider doing:
arr[arr_len] = item
it'll avoid the creation of a new array

Complexity:
O(N)

add_at(arr_len : felt, arr : felt*, index : felt, item : felt) -> (arr_len : felt, arr : felt*)

Creates a new array with the item at the index position.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified index - the index the item needs to be added
item - the felt that needs to be added

Returns:
arr_len - the length of the new array
arr - the new array

Remark:
Will fail if the array is empty or if the index is out of range.

Complexity:
O(N)

remove_first(arr_len : felt, arr : felt*) -> (arr_len : felt, arr : felt*)

Creates a new array without first item.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified

Returns:
arr_len - the length of the new array
arr - the new array

Remark:
Will fail if the array is empty

Complexity:
O(N)

remove_last(arr_len : felt, arr : felt*) -> (arr_len : felt, arr : felt*)

Creates a new array without last item.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified

Returns:
arr_len - the length of the new array
arr - the new array

Remark:
Will fail if the array is empty

Complexity:
O(N)

remove_at(arr_len : felt, arr : felt*, index : felt) -> (arr_len : felt, arr : felt*)

Creates a new array without the item at the position index.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
index - the index of the felt that needs to be removed

Returns:
arr_len - the length of the new array
arr - the new array

Remark:
Will fail if the array is empty or if the index is out of range.

Complexity:
O(N)

remove_first_occurence_of(arr_len : felt, arr : felt*, item : felt) -> (arr_len : felt, arr : felt*)

Creates a new array without the first occurence of item.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
item - the item that needs to be removed

Returns:
arr_len - the length of the new array
arr - the new array

Remark:
Will fail if the array is empty or if the index is out of range.

Complexity:
O(N)

remove_last_occurence_of(arr_len : felt, arr : felt*, item : felt) -> (arr_len : felt, arr : felt*)

Creates a new array without the last occurence of item.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
item - the item that needs to be removed

Returns:
arr_len - the length of the new array
arr - the new array

Remark:
Will fail if the array is empty.

Complexity:
O(N)

remove_all_occurences_of(arr_len : felt, arr : felt*, item : felt) -> (arr_len : felt, arr : felt*)

Creates a new array without all occurences of item.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
item - the item that needs to be removed

Returns:
arr_len - the length of the new array
arr - the new array

Remark:
Will fail if the array is empty.

Complexity:
O(N)

sort(arr_len : felt, arr : felt*) -> (arr_len : felt, arr : felt*)

Creates a new array sorted from the biggest felt to the smallest felt.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified

Returns:
arr_len - the length of the new array
arr - the new array

Complexity:
O(N log(N))

reverse(arr_len : felt, arr : felt*) -> (arr_len : felt, arr : felt*)

Creates a new array that is the reverse of the arr given as parameter.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified

Returns:
arr_len - the length of the new array
arr - the new array

Complexity:
O(N)

join(arr1_len : felt, arr1 : felt*, arr2_len : felt, arr2 : felt*) -> (arr_len : felt, arr : felt*)

Creates a new array that will join the arr1 with arr2 by putting all elements of arr1 in an array then adding all elements of arr2.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified

Returns:
arr1_len - the length of the first array
arr1 - the first array
arr2_len - the length of the second array
arr2 - the second array

Complexity:
O(2N)

copy_from_to(arr_len : felt, arr : felt*, from_index : felt, to_index : felt) -> (arr_len : felt, arr : felt*)

Creates a new array that will copy the elements of the arr from (from_index included) an index to (to_index excluded) another index.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
from_index - the starting array the items needs to be copied from
to_index - the last index the copy must stop (can also be seen as number of elements to copy)

Returns:
arr_len - the length of the new array
arr - the new array

Remark:
Will fail if:

the to_index is smaller or equal to the from_index
the from_index or to_index is out of range

Complexity:
O(N)

replace(arr_len : felt, arr : felt*, old_item : felt, new_item : felt) -> (arr_len : felt, arr : felt*)

Creates a new array with all occurences of old_item replaced with another value new_item.

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
old_item - the old value that needs to be replaced
new_item - the new value that the old value will be replaced with

Returns:
arr_len - the length of the new array
arr - the new array

Complexity:
O(N)

Array searching functions

contains(arr_len : felt, arr : felt*, item : felt) -> (contains : felt)

Will check if arr contains the item

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
item - the item that needs to be looked for

Returns:
contains - 1 if contains the item otehrwise 0

Complexity:
O(N)

index_of(arr_len : felt, arr : felt*, item : felt) -> (index : felt)

Will check if arr contains the item and return its index

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
item - the item that needs to be looked for

Returns:
index - the index of the item or 3618502788666131213697322783095070105623107215331596699973092056135872020480

Remark:
It can return 3618502788666131213697322783095070105623107215331596699973092056135872020480 if the item isn't found (which is -1 in felt value)

Complexity:
O(N)

min(arr_len : felt, arr : felt*) -> (min : felt)

Will return the minimum value ot the arr

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
Returns:
min - the minimum value of the array

Remark:
Will fail if the array is empty

Complexity:
O(N)

index_of_min(arr_len : felt, arr : felt*) -> (index : felt)

Will return the index of the minimum value ot the arr

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
Returns:
index - the index of the minimum value of the array

Remark:
Will fail if the array is empty

Complexity:
O(N)

max(arr_len : felt, arr : felt*) -> (max : felt)

Will return the maximum value ot the arr

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified

Returns:
max - the maximum value of the array

Remark:
Will fail if the array is empty

Complexity:
O(N)

index_of_max(arr_len : felt, arr : felt*) -> (index : felt)

Will return the index of the maximum value ot the arr

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified

Returns:
index - the index of the maximum value of the array

Remark:
Will fail if the array is empty

Complexity:
O(N)

occurrences_of(arr_len : felt, arr : felt*, item : felt) -> (occurrences : felt)

Will return all the occurences of the item

Parameters:
arr_len - the length of the array
arr - the array that needs to be modified
item - the item for which the occurences need to be counter

Returns:
occurences - the amount of time the item is present in the array

Complexity:
O(N)

gaetbout/starknet-array-manipulation

Array manipulation

Array searching

Tests

TODO

Detailed description

Array manipulation functions

Array searching functions