# 2011.final-value-of-variable-after-performing-operations

## Statement

• `++X``X++` 使变量 `X` 的值 `1`
• `–X``X–` 使变量 `X` 的值 `1`

``````输入：operations = ["–X","X++","X++"]

–X：X 减 1 ，X =  0 - 1 = -1
X++：X 加 1 ，X = -1 + 1 =  0
X++：X 加 1 ，X =  0 + 1 =  1
``````

``````输入：operations = ["++X","++X","X++"]

++X：X 加 1 ，X = 0 + 1 = 1
++X：X 加 1 ，X = 1 + 1 = 2
X++：X 加 1 ，X = 2 + 1 = 3
``````

``````输入：operations = ["X,X","–X","X–"]

X++：X 加 1 ，X = 0 + 1 = 1
++X：X 加 1 ，X = 1 + 1 = 2
–X：X 减 1 ，X = 2 - 1 = 1
X–：X 减 1 ，X = 1 - 1 = 0
``````

• `1 <= operations.length <= 100`
• `operations[i]` 将会是 `"++X"``"X++"``"–X"``"X–"`

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–"`.

## Solution

``````from typing import List

class Solution:
def finalValueAfterOperations(self, operations: List[str]) -> int:
def f(s):
if "+" in s:
return 1
return -1
return sum(map(f, operations))
``````