Final Value of Variable After Performing Operations in Python

Problem Description

So, you want to know the final value of a variable after performing a series of operations? The problem is simple: you start with a variable initialized to zero, and you have a list of operations that either increment or decrement this variable.

Imagine you’re at a party, and every time someone says “Let’s have another drink!” (which is a + operation), you add another drink to your tally. But then, your friend says, “No more drinks for you!” (which is a - operation), and you have to subtract one from your tally. By the end of the night, you want to know how many drinks you actually had.

Code Solution

class Solution:
    def finalValueAfterOperations(self, operations: list[str]) -> int:
        return sum(op[1] == '+' or -1 for op in operations)

Approach

The approach here is straightforward. We loop through each operation in the list and check if it’s an increment (+) or a decrement (-). If it’s an increment, we add 1; if it’s a decrement, we subtract 1. The final result is simply the sum of all these operations.

Time and Space Complexity

Complexity Type	Complexity
Time Complexity	O(n), where n is the number of operations.
Space Complexity	O(1), as we are using a constant amount of space.

Real-World Example

Let’s say you’re managing your expenses for the month. You start with $0. Every time you buy something, you subtract from your total (a - operation), and every time you receive money (like a paycheck), you add to your total (a + operation). By the end of the month, you want to know how much money you have left.