Project Euler Problem 99 Largest exponential

Largest exponential

Problem 99

Comparing two numbers written in index form like 211 and 37 is not difficult, as any calculator would confirm that 211 = 2048 < 37 = 2187.

However, confirming that 632382518061 > 519432525806 would be much more difficult, as both numbers contain over three million digits.

Using
base_exp.txt (right click and 'Save Link/Target As...'), a 22K text file containing one thousand lines with a base/exponent pair on each line, determine which line number has the greatest numerical value.

NOTE: The first two lines in the file represent the numbers in the example given above.

C++:
#include <iostream>
#include <cmath>
#include <string>
#include <fstream>

using namespace std;

int main()
{
long b, e, max, temp;
int ans=0, no=0;
string filename;

cin >> filename;
ifstream inf(filename, ios::in);

char c;
while(inf >> b >> c >> e) {
no++;
temp = (long) (e * log(b));
if(temp > max) {
max = temp;
ans = no;
}
}

cout << ans << endl;

inf.close();

return 0;
}