ヤフーの面接問題-10進数(long型)をそれぞれバイナリと16進数で出力し、printfシリーズは使用できません...

プログラミング実装:10進数(long型)をそれぞれバイナリと16進数で出力し、printfシリーズは使用できません.
unsigned long型の変換を実現した.

//          ，      1bit       1   
char *int_to_bin(unsigned long data)
{
    int bit_num = sizeof(unsigned long) * 8;
    char *p_bin = new char[bit_num+1];
    p_bin[bit_num] = '\0';
    for (unsigned int i = 0; i < bit_num; ++i)
    {
        p_bin[i] = data << i >> (bit_num-1);
        if (p_bin[i] == 0)
            p_bin[i] = '0';
        else if (p_bin[i] == 1)
            p_bin[i] = '1';
        else
            p_bin[i] = 'a';
    }
    return p_bin;
}

//           ，      4bit        1   
char *int_to_hex(unsigned long data)
{
    int bit_num = sizeof(unsigned long) * 8;
    char *p_hex = new char[sizeof(unsigned long)*8/4+3];
    p_hex[0] = '0';
    p_hex[1] = 'x';
    p_hex[bit_num/4+2] = '\0';
    char *p_tmp = p_hex + 2;
    for (unsigned int i = 0; i < bit_num/4; ++i)
    {
        p_tmp[i] = data << (4*i) >> (bit_num-4);
        if (p_tmp[i] >= 0 && p_tmp[i] <= 9)
            p_tmp[i] += '0';
        else if (p_tmp[i] >= 10 && p_tmp[i] <= 15)
            p_tmp[i] = p_tmp[i] - 10 + 'A';
    }
    return p_hex;
}