[LeetCode] Baseball Game 棒球游戲

 

You're now a baseball game point recorder.

Given a list of strings, each string can be one of the 4 following types:

1. Integer (one round's score): Directly represents the number of points you get in this round.
2. "+" (one round's score): Represents that the points you get in this round are the sum of the last two validround's points.
3. "D" (one round's score): Represents that the points you get in this round are the doubled data of the last valid round's points.
4. "C" (an operation, which isn't a round's score): Represents the last valid round's points you get were invalid and should be removed.

 

Each round's operation is permanent and could have an impact on the round before and the round after.

You need to return the sum of the points you could get in all the rounds.

Example 1:

Input: ["5","2","C","D","+"]
Output: 30
Explanation: 
Round 1: You could get 5 points. The sum is: 5.
Round 2: You could get 2 points. The sum is: 7.
Operation 1: The round 2's data was invalid. The sum is: 5.  
Round 3: You could get 10 points (the round 2's data has been removed). The sum is: 15.
Round 4: You could get 5 + 10 = 15 points. The sum is: 30.

 

Example 2:

Input: ["5","-2","4","C","D","9","+","+"]
Output: 27
Explanation: 
Round 1: You could get 5 points. The sum is: 5.
Round 2: You could get -2 points. The sum is: 3.
Round 3: You could get 4 points. The sum is: 7.
Operation 1: The round 3's data is invalid. The sum is: 3.  
Round 4: You could get -4 points (the round 3's data has been removed). The sum is: -1.
Round 5: You could get 9 points. The sum is: 8.
Round 6: You could get -4 + 9 = 5 points. The sum is 13.
Round 7: You could get 9 + 5 = 14 points. The sum is 27.

 

Note:

• The size of the input list will be between 1 and 1000.
• Every integer represented in the list will be between -30000 and 30000.

 

這道題不是一道難題，直接按照題目的描述來分情況處理即可，博主開始在取數組的最后一個數和倒數第二個數的時候還做了數組為空檢測，但是的貌似這道題默認輸入都是合法的，不會存在上一輪不存在還要取值的情況，那就不用檢測啦，代碼就更加的簡潔啦：

 

class Solution {
public:
    int calPoints(vector<string>& ops) {
        vector<int> v;
        for (string op : ops) {
            if (op == "+") {
                v.push_back(v.back() + v[v.size() - 2]);
            } else if (op == "D") {
                v.push_back(2 * v.back());
            } else if (op == "C") {
                v.pop_back();
            } else {
                v.push_back(stoi(op));
            }
        }
        return accumulate(v.begin(), v.end(), 0);
    }
};

 

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