Poj 1546

#include <iostream>
#include <string>
#include <iomanip>
using namespace std;

int charToNum(char element)
{
	if(element <= '9')
		return element - '0';
	else if(element <= 'Z' && element >= 'A')
		return element - 'A' + 10;
	else if(element <= 'z' && element >= 'a')
		return element - 'a' + 36;
}

char numToChar(int num)
{
	if(num <= 9)
		return num + '0';
	else if(num <= 35 && num >= 10)
		return num - 10 + 'A';
	else if(num <=61 && num >= 36)
		return num - 36 + 'a';
}

string divide(const string& sequence, int sourceBase, int targetBase, string& modeResult)
{
	if(sequence.find_first_not_of('0') == string::npos)
		return "";

	string result;
	int mode = 0;
	for(int i = 0 ; i < sequence.length(); i++)
	{
		int value = charToNum(sequence[i]) + sourceBase * mode;
		mode = value % targetBase;
		value = value / targetBase;
		result += numToChar(value);
	}
	modeResult = numToChar(mode) + modeResult;
	divide(result, sourceBase, targetBase, modeResult);
	return result;
}

string convertBase(const string& sequence, int sourceBase, int targetBase)
{
	if(sequence == "0")
		return "0";
	string targetSequence;
	divide(sequence, sourceBase, targetBase, targetSequence);
	return targetSequence;
}

int main()
{
	int sourceBase, targetBase;
	string sourceSequence, targetSequence;
	while(cin >> sourceSequence >> sourceBase >> targetBase)
	{
		targetSequence = convertBase(sourceSequence, sourceBase, targetBase);
		if(targetSequence.length() > 7)
			targetSequence = "ERROR";
		cout << setw(7) <<targetSequence << endl;
	}
}