剑指 Offer II 栈

036. 后缀表达式

class Solution {
   Stacknums=new Stack();
    public int evalRPN(String[] tokens) {
        for(String x: tokens)
        {
            char k=x.charAt(0);
            if(x.equals("+")||x.equals("-")||x.equals("*")||x.equals("/"))
            {
                int b=nums.pop(),a=nums.pop();
              if(x.equals("+"))a+=b;
             if(x.equals("-"))a-=b;
              if(x.equals("*"))a*=b;
               if(x.equals("/"))a/=b;
               nums.push(a);
            }
            else nums.push(Integer.parseInt(x));          
        }
        return nums.pop();
    }
}