华为面试题：
char *mystrcpy(char *dest,char *src,int n)
{
char *newdest = dest;
assert((dest != NULL) && (src != NULL))
while (n &&((*dest++ = *src++) != '\0'))
{
n--;
}
if (n)
{
while (--n)
*dest = '\0';
}
return newdest;
}
