How to define a recursive function to merge two sorted lists and return a new list with a increasing order in Python?

Question

I want to define a recursive function to merge two sorted lists (these two lists are sorted) and return a new list containing all the values in both argument lists with a incre

Answer 1

def combine(a,b):
    if not a and not b: return []
    if not a: return [b[0]] + combine(a, b[1:])
    if not b: return [a[0]] + combine(a[1:], b)
    if a[0] > b[0]:
        return [b[0]] + combine(a, b[1:])
    return [a[0]] + combine(a[1:], b)

Your test case:

In [2]: a = [1,2,3,4]

In [3]: b = [5,6,7,8]

In [4]: combine(a,b)
Out[4]: [1, 2, 3, 4, 5, 6, 7, 8]

Another test case:

In [24]: a
Out[24]: [1, 2, 3, 8, 9]

In [25]: b
Out[25]: [1, 3, 5, 6, 7]

In [26]: combine(a,b)
Out[26]: [1, 1, 2, 3, 3, 5, 6, 7, 8, 9]