学习任务依旧栈的经典应用。 题目链接https://leetcode.cn/problems/basic-calculator-ii/description/ 优秀题解https://leetcode.cn/problems/basic-calculator-ii/solutions/91271/chai-jie-fu-za-wen-ti-shi-xian-yi-ge-wan-zheng-ji-/class Solution { public: int calculate(string s) { vectorint stk; char preSign ; int num 0; int n s.length(); for (int i 0; i n; i) { if (isdigit(s[i])) { num num * 10 int(s[i] - 0); } if (!isdigit(s[i]) s[i] ! || i n - 1) { switch (preSign) { case : stk.push_back(num); break; case -: stk.push_back(-num); break; case *: stk.back() * num; break; default: stk.back() / num; } preSign s[i]; num 0; } } return accumulate(stk.begin(), stk.end(), 0); } };