I wrote the following accepted solution for the Decode Ways problem(https://leetcode.com/problems/decode-ways/):
class Solution:
def numDecodings(self, s: str) -> int:
l2 = [0, 1]
ldig = None
for i,val in enumerate(s):
curr = 0
cdig = int(val)
if cdig: curr += l2[1]
if ldig and 10*ldig + cdig < 27: curr += l2[0]
del l2[0]
l2.append(curr)
ldig = cdig
return len(s) and l2[1]
On the last line I am capturing the case where the input string s is empty. I've seen other people doing this and it works - the code returns zero when the input is empty, otherwise it returns the calculated value l2[1]. Yet, I still don't understand why does such a construct work in python?
In my mind the expression
len(s) and l2[1]
is just a boolean and thus the function shall return true or false. Instead it returns an integer which can be different from 0 or 1.
Can someone explain why this works? Or point to the relevant location in the documentation?
