#include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
         using namespace std;class Solution {public:	// 参考：http://zh.wikipedia.org/wiki/逆波兰表示法 即可	int evalRPN(vector
         
           &tokens) { stack
          
            stk; for (int i = 0; i < tokens.size(); ++i) { string word = tokens[i]; char ch = word[0]; if (word.size() > 1 || isdigit(ch)) stk.push(str2int(word)); else { int val2 = stk.top(); stk.pop(); int val1 = stk.top(); stk.pop(); if (ch == '+') stk.push(val1 + val2); else if (ch == '-') stk.push(val1 - val2); else if (ch == '*') stk.push(val1 * val2); else if (ch == '/') stk.push(val1 / val2); } } return stk.top(); } int str2int(string& s) { int res = 0, flag = 1, i = 0; if (!isdigit(s[0])) { flag = s[0] == '+' ? 1 : -1; ++i; } for (; i < s.size(); ++i) res = res * 10 + (s[i] - '0'); return res*flag; }};