Auto comment: topic has been updated by jay__0208 (previous revision, new revision, compare).

For 1, I think it's PyPy.

I tested the code in custom test. With Python 3.7.2 I got 124ms, but with PyPy 3.6 I got 2261ms.

For 2, It's $$$\mathcal{O}(n^2)$$$. string::operator= is $$$\mathcal{O}(n)$$$ and you used it $$$\mathcal{O}(n)$$$ times. The correct way is using string::operator+=.

The runtime of Python string concatenation is the length of the combined string, not O(1)

https://stackoverflow.com/questions/37133547/time-complexity-of-string-concatenation-in-python

You code therefore runs in O(n2).

You will get familiar with Python data structures over time. Today I learnt how to call a function recursively in Codeforces.

In python, strings are immutable.

When you concatenate strings then it creates a new instance. So every time you add a character to a string it creates a new instance of that string which takes O(n) time. And you do this n times so O(n*n). It's always better to use list instead of string in such cases.

for _ in range (int(input())):
        n=int(input())
        l=math.ceil(n/4)
        ans='9'*(n-l)+'8'*l
        print(ans)

for _ in range (int(input())):
        n=int(input())
        l=math.ceil(n/4)
        ans=[]
        for i in range(n-l): ans.append('9')
        for i in range(l): ans.append('8')
        print("".join(ans))

https://mirror.codeforces.com/contest/1388/submission/88530339

https://mirror.codeforces.com/contest/1388/submission/88530040

Might help

Please don't shout.