leetcode

0 class Solution {

1 bool is_op(const string &s) { return s == "+" || s == "-" || s == "*" || s == "/"; }

2

3 public:

4 int evalRPN(vector<string> &tokens) {

5 if (tokens.size() == 0) return 0;

6

7 stack<long long> st;

8 for (string &s : tokens) {

9 if (is_op(s)) {

10 long long y = st.top();

11 st.pop();

12 long long x = st.top();

13 st.pop();

14 switch (s[0]) {

15 case '+': st.push(x + y); break;

16 case '-': st.push(x - y); break;

17 case '*': st.push(x * y); break;

18 case '/': st.push(x / y); break;

19 }

20 } else

21 st.push(stoi(s));

22 }

23 return st.top();

24 }

25 };