leetcode--Evaluate Reverse Polish Notation

class Solution {
public:
    int evalRPN(vector<string>& tokens) {
        stack<int> number;
        
        for(int i = 0 ; i < tokens.size();i++)
        {
            if(tokens[i] == "+" || tokens[i] == "-" || tokens[i] == "*" || tokens[i] == "/")
            {
                int n1 = 0;
                int n2 = 0;
                n1 = number.top();
                number.pop();
                n2 = number.top();
                number.pop();
                if(tokens[i] == "+")
                    number.push(n1+n2);
                else if(tokens[i] == "-")
                    number.push(n2-n1);
                else if(tokens[i] == "*")
                    number.push(n1*n2);
                <span style="color:#ff0000;">else if(tokens[i] == "/")</span>

<span style="color:#ff0000;">                 {// </span>

<span style="color:#ff0000;">                    if(n1 != 0)</span>

<span style="color:#ff0000;">                      number.push(n2/n1);</span>

                 }
                   
               
            }
            else
            {
                number.push(atoi(tokens[i].c_str()));
            }
        }

        if(!number.empty())// 
          return number.top();
        
    }
};