LeetCode 682. Baseball Game

682. Baseball Game

解析

简化版的中缀表达式转后缀表达式。

class Solution {
public:
    int calPoints(vector<string>& ops) {
        int sum=0;
        int point=0;
        int point2 = 0;
        std::stack<int> Stack;
    for (auto x : ops) {
        if (x[0] =='-' || isdigit(x[0])) {
            point = stoi(x);
            sum += point;
            Stack.push(point);
        }
        else if (x[0] == '+') {
            point = Stack.top();
            Stack.pop();
            point2 = Stack.top();
            Stack.pop();
            sum += (point + point2);
            Stack.push(point2);
            Stack.push(point);
            Stack.push(point + point2);
        }
        else if (x[0] == 'D') {
            point = Stack.top() * 2;
            Stack.pop();
            sum += point;
            Stack.push(point / 2);
            Stack.push(point);
        }
        else if (x[0] == 'C') {
            point = Stack.top();
            Stack.pop();
            sum -= point;
        }
    }
        return sum;
    }
};