如何仅使用 sscanf 从字符串中提取所有数字? [英] How to extract all Numbers out of a String using sscanf only?
问题描述
如何在 C ONLY 中使用 sscanf 从具有以下格式的字符串中提取所有数字:
How to extract all Numbers out of a String with following format using sscanf in C ONLY:
" (3, 2, 4,5, 10 )"
" (3, 2, 4,5, 10 )"
空格可以无处不在，但不能在数字之间.每个位置可以有 0 个或更多空格.
Whitespaces can be everywhere but not between Digits of course. There can be 0 Whitespaces or more at every position.
字符串必须具有正确的格式，否则会出错.例如，" (3,2, " 是一个错误.每个不是空格或格式的一部分的字符都是错误
The String has to have the right format or its an error. " (3,2, " is an error for example. Every Character that's not an whitespace or part of the format is an error
仅使用 sscanf(它不是可选的)
Using only sscanf (its not optional)
我的想法当然是用sscanf进行while循环，但格式是我的问题
My Idea, of course, is to while loop with sscanf, but the formatting is my problem
括号内的数字数量可以不同.所以我们可以在括号内有 0 个数字或 n 个数字.n 是任意数字.(a,a+1,...,a+n).
The Amount of number inside the brackets can be different. So we can have 0 Numbers or n Numbers inside the brackets. with n being any number. (a,a+1,...,a+n).
当然允许使用 stdio.h 中包含的所有内容，但不允许使用扩展库
Of course its allowed to use everything included in stdio.h, but no extendet librarys
推荐答案
序言
似乎可以将数据的格式概括为:随处留白；左括号后跟一个或多个纯整数(无符号，无小数点)的序列，由逗号分隔并以右括号结尾.或者，( 和 ) 之间可能有零个整数.
Preamble
It seems that the format of the data can be summarized as: white space anywhere; open parenthesis followed by a sequence of one or more plain integers (no signs, no decimal points) separated by commas and terminated by a close parenthesis. Alternatively, there could be zero integers between ( and ).
必须使用sscanf()处理数据；没有关于对 sscanf() 的单个调用的规定规则.与文件 I/O 替代方案(scanf()、fscanf() 等)相比，使用 sscanf() 的优点之一是如有必要，您可以重试扫描.
The data must be processed using sscanf(); there is no stated rule about a single call to sscanf(). One of the advantages of using sscanf() over the file I/O alternatives (scanf(), fscanf(), etc) is that you can retry a scan if necessary.
请注意，scanf() 系列不能很好地处理可选项目".空格大部分是微不足道的——除了 %c、%[…](扫描集)和 %n 之外的所有转换说明符都跳过前导空格，并且格式字符串中的空白字符与输入中的零个或多个空白字符匹配.
Note that the scanf() family does not handle 'optional item' very well. White space is mostly trivial — all conversion specifiers except %c, %[…] (scan sets) and %n skip leading white space, and a white space character in a format string matches zero or more white space characters in the input.
函数 string_analyzer() 完成这项工作；它有一个适度复杂的接口，因为它本身不进行 I/O——它分析字符串并将数字添加到传递给函数的数组结构中.它还设置了一条消息，告诉调用者出了什么问题.其他函数是支持函数(用于 struct int_array 类型)和测试工具(main() 加 test_string_analyzer()).>
The function string_analyzer() does the job; it has a modestly complex interface because it does no I/O itself — it analyzes the string and adds the numbers to an array structure that is passed into the function. It also sets a message that tells the caller a bit about what went wrong. The other functions are support functions (for the struct int_array type) and the test harness (main() plus test_string_analyzer()).
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct int_array
{
char *base;
size_t maxlen;
size_t curlen;
};
static void dump_int_array(const char *tag, const struct int_array *array);
static void add_to_int_array(struct int_array *array, int data);
static void free_int_array(struct int_array *array);
static void test_string_analyzer(const char *str);
static int string_analyzer(const char *str, struct int_array *array, char **msg)
{
int offset;
int length = strlen(str);
int data;
char trailer;
if (sscanf(str, " ( %[)] %n", &trailer, &offset) == 1)
{
/* Empty list */
assert(trailer == ')');
if (offset == length)
{
*msg = "it is an empty list";
return 0;
}
else
{
*msg = "it has extra characters after an empty list";
return -1;
}
}
if (sscanf(str, " ( %d %c%n", &data, &trailer, &offset) != 2 ||
(trailer != ',' && trailer != ')'))
{
*msg = "it does not start correctly";
return -1;
}
add_to_int_array(array, data);
if (trailer == ')' && offset == length)
{
*msg = "it is valid";
return 0;
}
const char *source = str + offset;
while (sscanf(source, "%d %[,)] %n", &data, &trailer, &offset) == 2)
{
add_to_int_array(array, data);
length = strlen(source);
if (trailer == ')' && offset == length)
{
*msg = "it is valid";
return 0;
}
else if (trailer == ')')
{
*msg = "it does not end correctly";
return -1;
}
source += offset;
}
*msg = "it is incorrectly formatted";
return -1;
}
int main(void)
{
const char *samples[] =
{
/* Valid */
" (3, 2, 4,5, 10 )",
" ( 4 , 6 ) ",
"(4)",
"()",
/* random -n 15 10 99 | commalist -t -B 8 -b '"( ' -T ' )",' */
"( 65, 83, 81, 60, 61, 23, 48, 89, 67, 27, 73, 25, 92, 13, 67 )",
/* Invalid */
" (3,2, ",
"3,2",
" (3,2,1) apathy",
" () apathy",
" (3,X,1)",
" (3X,1)",
};
enum { NUM_SAMPLES = sizeof(samples) / sizeof(samples[0]) };
for (int i = 0; i < NUM_SAMPLES; i++)
test_string_analyzer(samples[i]);
return 0;
}
static void test_string_analyzer(const char *str)
{
struct int_array array = { 0, 0, 0 };
char *msg = 0;
printf("Analyzing [%s]\n", str);
int rc = string_analyzer(str, &array, &msg);
if (rc == 0)
printf("String '%s' OK: %s\n", str, msg);
else
printf("String '%s' is misformatted: %s\n", str, msg);
dump_int_array("List contents", &array);
free_int_array(&array);
}
static void dump_int_array(const char *tag, const struct int_array *array)
{
int length = printf("%s (%zu): ", tag, array->curlen);
const char *pad = "";
for (size_t i = 0; i < array->curlen; i++)
{
length += printf("%s%d", pad, array->base[i]);
pad = ", ";
if (length >= 64)
{
pad = " ";
length = 0;
putchar('\n');
}
}
if (length > 0)
putchar('\n');
}
static void add_to_int_array(struct int_array *array, int data)
{
if (array->curlen >= array->maxlen)
{
assert(array->curlen == array->maxlen);
size_t newlen = array->maxlen * 2 + 2;
void *newarr = realloc(array->base, newlen * sizeof(array->base[0]));
if (newarr == NULL)
{
}
array->base = newarr;
array->maxlen = newlen;
}
array->base[array->curlen++] = data;
}
static void free_int_array(struct int_array *array)
{
free(array->base);
array->base = 0;
array->maxlen = 0;
array->curlen = 0;
}
示例输出:
Analyzing [ (3, 2, 4,5, 10 )]
String ' (3, 2, 4,5, 10 )' OK: it is valid
List contents (5): 3, 2, 4, 5, 10
Analyzing [ ( 4 , 6 ) ]
String ' ( 4 , 6 ) ' OK: it is valid
List contents (2): 4, 6
Analyzing [(4)]
String '(4)' OK: it is valid
List contents (1): 4
Analyzing [()]
String '()' OK: it is an empty list
List contents (0):
Analyzing [( 65, 83, 81, 60, 61, 23, 48, 89, 67, 27, 73, 25, 92, 13, 67 )]
String '( 65, 83, 81, 60, 61, 23, 48, 89, 67, 27, 73, 25, 92, 13, 67 )' OK: it is valid
List contents (15): 65, 83, 81, 60, 61, 23, 48, 89, 67, 27, 73, 25
92, 13, 67
Analyzing [ (3,2, ]
String ' (3,2, ' is misformatted: it is incorrectly formatted
List contents (2): 3, 2
Analyzing [3,2]
String '3,2' is misformatted: it does not start correctly
List contents (0):
Analyzing [ (3,2,1) apathy]
String ' (3,2,1) apathy' is misformatted: it does not end correctly
List contents (3): 3, 2, 1
Analyzing [ () apathy]
String ' () apathy' is misformatted: it has extra characters after an empty list
List contents (0):
Analyzing [ (3,X,1)]
String ' (3,X,1)' is misformatted: it is incorrectly formatted
List contents (1): 3
Analyzing [ (3X,1)]
String ' (3X,1)' is misformatted: it does not start correctly
List contents (0):
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