雅虎面试题─把十进制数(long型)分别以二进制和十六进制形式输出，不能使用printf系列

编程实现：把十进制数(long型)分别以二进制和十六进制形式输出，不能使用printf系列。

实现了unsigned long型的转换。

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// 十进制转换为二进制，十进制数的每1bit转换为二进制的1位数字

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;

}

// 十进制转换为十六进制，十进制数的每4bit转换为十六进制的1位数字

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;

}