自定义函数实现10进制转化为16进制

把结果都列出来，可以提升代码运行速率

#include<stdio.h>

char hex_char(unsigned int n)
{
    switch(n)
    {
        case 0:
            return \'0\';
        case 1:
            return \'1\'; 
        case 2:
            return \'2\';
        case 3:
            return \'3\';
        case 4:
            return \'4\';
        case 5:
            return \'5\'; 
        case 6:
            return \'6\';
        case 7:
            return \'7\';
        case 8:
            return \'8\';
        case 9:
            return \'9\'; 
        case 10:
            return \'a\';
        case 11:
            return \'b\';
        case 12:
            return \'c\';
        case 13:
            return \'d\'; 
        case 14:
            return \'e\';
        case 15:
            return \'f\';                       
    }
        return 0;
}

void int_hex(unsigned int n)
{
    int i = n % 16;   
    if(n >= 16)
       int_hex(n / 16);
    printf("%c", hex_char(i));   //后序输出    
} 

int main()
{
    /*int a = 20;
    printf("%x\n", a);   //%x直接输出16进制 
    return 0;
    */
    int a = 15;
    scanf("%d", &a);    
    int_hex(a);    //void的函数直接调用 
    printf("%c", a);   //%c输出单个字符 
    return 0;
}