题目

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--".

解题思路

就是创建一个变量X模拟加和减的过程

代码

Python

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class Solution:
    def finalValueAfterOperations(self, operations: List[str]) -> int:
        return sum(1 if op[1] == '+' else -1 for op in operations)

C++

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class Solution {
public:
    int finalValueAfterOperations(vector<string>& operations) {
        int ans = 0;
        for (auto s: operations){
            for (auto c: s){
                if (c =='+') {
                    ans++;
                    break;
                }
                else if (c == '-') {
                    ans--;
                    break;
                }
            }
        }
        return ans;
    }
};

Go

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func finalValueAfterOperations(operations []string) int {
    ans := 0
    for _, s:= range operations{
        for _, c:= range s{
            if c == '+'{
                ans++
                break
            } else if c == '-'{
                ans--
                break
            }
        }
    }
    return ans
}