# LeetCode 2011. Final Value of Variable After Performing Operations

## Description

https://leetcode.com/problems/final-value-of-variable-after-performing-operations/

There is a programming language with only four operations and one variable `X`:

• `++X` and `X++` increments the value of the variable `X` by `1`.
• `--X` and `X--` decrements the value of the variable `X` by `1`.

Initially, the value of `X` is `0`.

Given an array of strings `operations` containing a list of operations, return the final value of `X` after performing all the operations.

Example 1:

```Input: operations = ["--X","X++","X++"]
Output: 1
Explanation: The operations are performed as follows:
Initially, X = 0.
--X: X is decremented by 1, X =  0 - 1 = -1.
X++: X is incremented by 1, X = -1 + 1 =  0.
X++: X is incremented by 1, X =  0 + 1 =  1.
```

Example 2:

```Input: operations = ["++X","++X","X++"]
Output: 3
Explanation: The operations are performed as follows:
Initially, X = 0.
++X: X is incremented by 1, X = 0 + 1 = 1.
++X: X is incremented by 1, X = 1 + 1 = 2.
X++: X is incremented by 1, X = 2 + 1 = 3.
```

Example 3:

```Input: operations = ["X++","++X","--X","X--"]
Output: 0
Explanation: The operations are performed as follows:
Initially, X = 0.
X++: X is incremented by 1, X = 0 + 1 = 1.
++X: X is incremented by 1, X = 1 + 1 = 2.
--X: X is decremented by 1, X = 2 - 1 = 1.
X--: X is decremented by 1, X = 1 - 1 = 0.
```

Constraints:

• `1 <= operations.length <= 100`
• `operations[i]` will be either `"++X"``"X++"``"--X"`, or `"X--"`.

## Explanation

Base on the operation to increase the value.

## Python Solution

``````class Solution:
def finalValueAfterOperations(self, operations: List[str]) -> int:
x = 0

for operation in operations:
if operation == '++X' or operation == 'X++':
x += 1
elif operation == '--X' or operation == 'X--':
x -= 1

return x``````
• Time Complexity: O(N).
• Space Complexity: O(N).