输入十进制数，输出其相对应的16进制数。

解法如下：

#include <vector>
#include <iostream>
#include <string>

using namespace std;

string hex2string(unsigned char t)
{
	string str;

	int p = (t & 0xF0) >> 4;
	if (p >= 0 && p <= 9)
		str += p + '0';
	else
		str += p - 10 + 'A';

	p = t & 0x0F;
	if (p >= 0 && p <= 9)
		str += p + '0';
	else
		str += p - 10 + 'A';

	return str;
}

void format(vector<int>&v)
{
	int t = 0;
	for (int i = v.size() - 1; i >= 0; --i) {
		v[i] += t;
		t = v[i] / 256;
		v[i] %= 256;
	}
}

void mul10n(vector<int>& v, int p, int n)
{// v = p * 10^n
	for (int i = 0; i < v.size(); ++i) {
		v[i] = 0;
	}


	v[v.size() - 1] = p;

	while (n-- > 0) {
		for (int i = v.size() - 1; i >= 0; --i) {
			v[i] *= 10;
		}
		format(v);
	}
}

int main()
{
	string str = "123456789";
	while (cin >> str) {
		vector<int> v(str.size()/2, 0);

		vector<int> v2;
		v2.resize(v.size());

		for (int j  = 0; j < str.size(); ++j) {
			mul10n(v2, str[str.size() - j - 1] - '0', j);
			for (int i = 0; i < v.size(); ++i) {
				v[i] += v2[i];
			}

			format(v);
		}

//		cout << str << ":";
		for (int i = 0; i < v.size(); ++i)
			cout << hex2string(v[i]); 
		cout << endl;
	}
	
	return 0;
}