递归地将数字添加到排序列表

Question

I want to add my_num to where it fits in the given list and I want to solve it by using this structure, however I'm not getting the right results. What can I do?

my_lst   = [1, 3, 5]
my_num   = 4

def new_number(lst):
    return lst

def plus_number(n, lst):
    
    def add_number(n2, lst2):
        for i in range(len(lst)):
            if lst2[0] > n2:
                return [n2] + lst2
            else:
                return [lst[0]] + add_number(n2, lst2[1:])
    
    return new_number(add_number(n, lst))

result = plus_number(my_num, my_lst)

print(result)

>>> [1, 1, 4, 5]

Edit: changed [lst[0]] to [lst2[0]] and it works. Thanks!

Answer 1

There is already a stdlib method for this, no need to reinvent it:

>>> from bisect import insort
>>> my_lst = [1, 3, 5]
>>> insort(my_lst, 4)
>>> my_lst
[1, 3, 4, 5]

Answer 2

I've two solutions:

1. Using a sentinel, enumerate and insert.

my_lst = [1, 3, 5]
my_num = 4
my_lst.append(my_num) # sentinel
for i, value in enumerate(my_lst):
    if my_num <= value:
        my_lst.insert(i, my_num)
        break
my_lst.pop() # remove sentinel
print(my_lst)

2. Using enumerate, insert and else:

my_lst = [1, 3, 5]
my_num = 4
for i, value in enumerate(my_lst):
    if my_num <= value:
        my_lst.insert(i, my_num)
        break
else:
    my_lst.append(my_num)
print(my_lst)

If you can't use break, you can circumvent that with a function. Note that this will be trickier for the first function.