1： sprintf(), 字符串拼接， 返回值
spritnf 返回了本次函数调用最终打印到字符缓冲区中的字符数目。也就是说每当一次sprinf 调用结束以后，你无须再调用一次strlen 便已经知道了结果字符串的长度。
2： long int strtol(const char *nptr, char **endptr, int base)
The strtol() function converts the initial part of the string in nptr to a long integer value according to the given base, which must be between 2 and 36 inclusive, or be
the special value 0.
The string may begin with an arbitrary amount of white space (as determined by isspace(3)) followed by a single optional '+' or '-' sign. If base is zero or 16, the
string may then include a "0x" prefix, and the number will be read in base 16; otherwise, a zero base is taken as 10 (decimal) unless the next character is '0', in which
case it is taken as 8 (octal).
The remainder of the string is converted to a long int value in the obvious manner, stopping at the first character which is not a valid digit in the given base. (In
bases above 10, the letter 'A' in either upper or lower case represents 10, 'B' represents 11, and so forth, with 'Z' representing 35.)
If endptr is not NULL, strtol() stores the address of the first invalid character in *endptr. If there were no digits at all, strtol() stores the original value of nptr
in *endptr (and returns 0). In particular, if *nptr is not ' ' but **endptr is ' ' on return, the entire string is valid.
The strtoll() function works just like the strtol() function but returns a long long integer value