2011. Final Value of Variable After Performing Operations

Easy

題目描述

Description

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: nums = ["++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: nums = ["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--".

解答

Solution

/**
 * @param {string[]} operations
 * @return {number}
 */
var finalValueAfterOperations = function (operations) {
  let result = 0;

  for (let i = 0; i < operations.length; i++) {
    if (operations[i].includes("+")) {
      result++;
    } else {
      result--;
    }
  }

  return result;
};

解題思路

因為只會有 "++X", "X++", "--X", "X--" 四種狀況，所以可以簡單使用 .includes() 來判斷是加或減。

心得

滿直觀簡單的題目！