程序代码：

#include<stdio.h>
#include<string.h>
void itoh(int n,char *s)
{
    char base[16] = {'0','1','2','3',
                     '4','5','6','7',
                     '8','9','A','B',
                     'C','D','E','F'};
    int a = n;
    int i = 0;
    while(a != 0)
    {
        s[i++] = base[a%16];
        a/=16;
    }
}
main()
{
    int n = 43981;
    char a[80] = {0};
    itoh(n,a);
    for(int i = strlen(a)-1;i>=0;i--)
        printf("%c",a[i]);
    printf("\n");
}