Python Coding challenge - Day 526| What is the output of the following Python Code?

Code Explanation:

1. Function Definition

def rob(nums):

This defines a function called rob that takes a single parameter nums, which is a list of integers.

Each integer in nums represents the amount of money in a house.

The goal is to compute the maximum amount of money that can be robbed without robbing two adjacent houses.

2. Handle Empty Input

    if not nums:

        return 0

If the list nums is empty (i.e., there are no houses to rob), the function returns 0.

not nums is True when the list is empty.

3. Initialize State Variables

    a, b = 0, 0

These two variables represent the maximum money that can be robbed:

a: maximum money robbed up to the house before the previous one (i.e., i-2)

b: maximum money robbed up to the previous house (i.e., i-1)

Both are initially 0 since no money has been robbed yet.

4. Iterate Through Each House

    for n in nums:

This loop goes through each house (each value n in nums).

n represents the amount of money in the current house.

5. Update State Variables

        a, b = b, max(b, a + n)

This is the key logic of the algorithm.

Temporarily:

a becomes the previous value of b (previous house's max loot).

b becomes the max of:

b (not robbing current house, keep max so far)

a + n (rob current house, so we add its value to max loot up to i-2)

This ensures no two adjacent houses are robbed.

6. Return Final Result

    return b

After processing all houses, b holds the maximum money that can be robbed without violating the "no two adjacent houses" rule.

7. Function Call and Output

print(rob([2, 7, 9, 3, 1])) 

Calls the rob function with [2, 7, 9, 3, 1] as input.

Expected Output: 12

Rob house 1 (2), skip house 2, rob house 3 (9), skip house 4, rob house 5 (1) → 2 + 9 + 1 = 12

Output:

12