A linked list as a tuple Python-CodePudding

A connected list is given, which is implemented as a tuple (a number, link to the following pair) of the form in which the values are already sorted: x = (1, (3, (4, (7, (9, None) It is necessary to implement a function that reverses the list: example of a call: reverse((1, (3, (6, (8, None))))) Result: (8, (6, (3, (1, None))))

This is what i've done, i know it's incorrect cause first element would be doubled then

def reverse(linked_list: tuple):
    last_pair = (linked_list[0], None)
    while linked_list[1]:
        new_list = (linked_list[0], last_pair)
        return new_list
        return reverse(linked_list[1])

This is the result: (1, (1, None))

I have no idea how to do it in correct way, there is nothing about linked lists as tuples on the internet

CodePudding user response：

The implementation in the question does not evaluate all parts of the argument passed to reverse().

Here's one way to achieve your objective:

def reverse(t):
    result = None
    while True:
        a, b = t
        result = a, result
        if (t := b) is None:
            break
    return result
    
print(reverse((1, (3, (6, (8, None))))))

Output:

(8, (6, (3, (1, None))))

CodePudding user response：

If you supply an additional argument for "reverse" sequence you can also succeed with recursive function:

def reverse(linked_t: tuple, rev_seq=None):
    while linked_t[1] is not None:
        rev_seq = (linked_t[0], rev_seq)
        return reverse(linked_t[1], rev_seq)
    else:
        return linked_t[0], rev_seq


print(reverse((1, (3, (6, (8, None))))))

(8, (6, (3, (1, None))))