题目：

题解：

class Solution {
public:int evalRPN(vector<string>& tokens) {int n = tokens.size();vector<int> stk((n + 1) / 2);int index = -1;for (int i = 0; i < n; i++) {string& token = tokens[i];if (token.length() > 1 || isdigit(token[0])) {index++;stk[index] = atoi(token.c_str());} else {switch (token[0]) {case '+':index--;stk[index] += stk[index + 1];break;case '-':index--;stk[index] -= stk[index + 1];break;case '*':index--;stk[index] *= stk[index + 1];break;case '/':index--;stk[index] /= stk[index + 1];break;}}}return stk[index];}
};