LintCode 983: Baseball Game

最新推荐文章于 2019-11-02 16:56:22 发布

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本文介绍了一种用于棒球比赛计分的算法，该算法能够处理四种类型的输入：整数分数、加号（上两轮分数之和）、大写字母D（上一轮分数的两倍）和大写字母C（取消上一轮分数）。通过使用栈来存储每轮的有效分数，算法可以高效地计算所有有效分数的总和。

Baseball Game
You’re now a baseball game point recorder.

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

Integer (one round’s score): Directly represents the number of points you get in this round.
“+” (one round’s score): Represents that the points you get in this round are the sum of the last two valid round’s points.
“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.
“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
Example1:

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.
Example2:

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

代码如下：
注意：

对于数字的情况记得parse前面的’-’。
C++里面，integer转string用to_string(), string转integer用stoi()

class Solution {
public:
    /**
     * @param ops: the list of operations
     * @return:  the sum of the points you could get in all the rounds
     */
    int calPoints(vector<string> &ops) {
        
        int len = ops.size();
        if (len == 0) return 0;
        
        int sum = 0;
        stack<string> s;
        
        for (int i = 0; i < len; ++i) {
            if ((ops[i][0] >= '0' && ops[i][0] <= '9') || (ops[i][0] == '-')) {    //it is number   
                s.push(ops[i]);
                sum += stoi(ops[i]);
            } else if (ops[i][0] == 'C') {
                if (!s.empty()) {
                    int topNum = stoi(s.top());
                    s.pop();
                    sum -= topNum;
                }
            } else if (ops[i][0] == 'D') {
                if (!s.empty()) {
                    int num = stoi(s.top()) << 1;
                    s.push(to_string(num));
                    sum += num;
                }
            } else if (ops[i][0] == '+') {
                if (!s.empty()) {
                    int topNum = stoi(s.top());
                    s.pop();
                    if (!s.empty()) {
                        int addNum = stoi(s.top()) + topNum;
                        s.push(to_string(topNum));
                        s.push(to_string(addNum));
                        sum += addNum;
                    }
                }
            }  
        }
        
        return sum;
    }
};