Python Coding challenge - Day 580| What is the output of the following Python Code?

 

Code Explanation:

1. Function Definition with Memoization

def foo(n, cache={0: 1}):

Defines a function foo that calculates factorial of a number n.

cache is a default dictionary used to store already computed values (memoization).

Initially, it contains {0: 1} because 0! = 1.

2. Check if Result Already Cached

    if n not in cache:

Checks if n's factorial is already computed and saved in the cache.

If not, we need to compute it.

3. Recursive Calculation and Caching

        cache[n] = n * foo(n - 1)

If n is not in the cache:

Recursively call foo(n - 1) to get (n - 1)!

Multiply it by n to compute n!

Save it to cache[n] so it's not recomputed in the future.

4. Return Cached Result

    return cache[n]

Whether it was just computed or already existed, return cache[n].

5. Call and Print: foo(3)

print(foo(3))

What Happens:

3 not in cache

→ compute 3 * foo(2)

2 not in cache

→ compute 2 * foo(1)

1 not in cache

→ compute 1 * foo(0)

0 is in cache → 1

foo(1) = 1 * 1 = 1 → store in cache

foo(2) = 2 * 1 = 2 → store in cache

foo(3) = 3 * 2 = 6 → store in cache

Printed Output:

6

6. Call and Print: foo(2)

print(foo(2))

What Happens:

2 is already in cache from previous call.

Just return cache[2] = 2.

Printed Output:

2

Final Output

6

2

Download Book - 500 Days Python Coding Challenges with Explanation