2011. Final Value of Variable After Performing Operations.py

"""
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.

"""


class Solution(object):
    def finalValueAfterOperations(self, operations):
        res = 0
        for item in operations:
            if item == "--X" or item == "X--":
                res -= 1
            else:
                res += 1
        return res


solution = Solution()

assert solution.finalValueAfterOperations(["--X", "X++", "X++"]) == 1
assert solution.finalValueAfterOperations(["++X", "++X", "X++"]) == 3
assert solution.finalValueAfterOperations(["X++", "++X", "--X", "X--"]) == 0