main.cpp

// Source: https://leetcode.com/problems/final-value-of-variable-after-performing-operations
// Title: Final Value of Variable After Performing Operations
// Difficulty: Easy
// Author: Mu Yang <http://muyang.pro>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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--"`.
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#include <vector>

using namespace std;

class Solution {
 public:
  int finalValueAfterOperations(vector<string>& operations) {
    auto x = 0;
    for (auto& op : operations) {
      if (op[1] == '+') {
        ++x;
      } else {
        --x;
      }
    }
    return x;
  }
};