Bulls and Cows | LeetCode | Google | Python

Solving the popular bulls and cows problem on Leetcode asked in Google with time and space complexities explained.

[SagarSharma-usru]

Here the secret and guess strings are the same lengths, so n=m for the time and space complexities, now will be O(n), still linear.

[candymanful]

Thank you so much for this great explanation. I am having troubles in understanding this line:
if num in count_secret:
if count_secret[num] > 0:
cows += 1
count_secret[num] -= 1
Could you please explain as to why we are having the second if condition? Thank you.