Problem 81: Palindromic Squares

This one requires base conversion, but I'm basically testing every square from 1 to 300 (90 000 fits into a 32-bit signed int; no intervention required). I reverse the string and test if it matches. If so, print the number and its palindromic square, in the requested base.

/*
ID: victor4
PROG: palsquare
LANG: C++
*/
#include <iostream>
#include <fstream>
#include <string>

#include <algorithm>

using namespace std;

inline char to_char(int c){
 if(c >= 10) return c - 10 + 'A';
 return c + '0';
}

string tobase(int num, int base){
 string ret;
 int div = base;
 while(div < num)
  div *= base;
 for(div /= base;;){
  ret += to_char(num / div);
  // get remainder
  num = num % div;
  // next
  if(div < 2) break;
  div /= base;
 }
 return ret;
}

string reverse_str(string str){
 reverse(str.begin(), str.end());
 return str;
}

int main() {
 ofstream fout ("palsquare.out");
 ifstream fin ("palsquare.in");
 int base;
 fin >> base;
 
 for(int i = 1; i <= 300; ++i){
  string n = tobase(i, base), n2(tobase(i * i, base));
  if(n2 == reverse_str(n2))
   fout << n << " " << n2 << endl;
 }
 
 return 0;
}