【leetcode】Evaluate Reverse Polish Notation

#include<iostream>
#include<stack>
#include<string>
#include<vector>
using namespace std;

class Solution
{
public:
double fun(vector<string> a)
{
stack<string>result;
for(int i=0;i<a.size();i++)
{
cout<<a[i]<<endl;
if(!a[i].compare("+")||!a[i].compare("-")||!a[i].compare("*")||!a[i].compare("/"))
{
cout<<"lf"<<endl;
string c1=result.top();
result.pop();
string c2=result.top();
result.pop();
int m=stoi(c1);
int n=stoi(c2);;
int num;
if(a[i][0]=='+')
num=n+m;
else if(a[i][0]=='-')
num=n-m;
else if(a[i][0]=='*')
num=n*m;
else
num=n/m;

result.push(to_string(num));
}
else
{
cout<<"re"<<endl;
result.push(a[i]);
}
}
return stod(result.top());
}
};

void main()
{
Solution solution;
string arr[5]={"4", "13", "5", "/", "+"};
vector<string>a(arr,arr+5);
cout<<solution.fun(a)<<endl;
}