我有一个包含相邻数字和字母的大文本文档。 就这样， JACK1940383DAVID30284HAROLD68372TROY4392等
我如何在 C++ 中像下面这样拆分它
名单：杰克/1940383，大卫/30284，...
【问题讨论】：
isdigit 的结果改变状态时，我不会逐个字符地阅读字符串并分开。
您可以在循环中使用std::string::find_first_of() 和std::string::find_first_not_of()，使用std::string::substr() 提取每个片段，例如：
std::string s = "JACK1940383DAVID30284HAROLD68372TROY4392";
std::string::size_type start = 0, end;
while ((end = s.find_first_of("0123456789", start)) != std::string::npos) {
std::string name = s.substr(start, end-start);
start = end;
int number;
if ((end = s.find_first_not_of("0123456789", start)) != std::string::npos) {
number = std::stoi(s.substr(start, end-start));
}
else {
number = std::stoi(s.substr(start));
}
start = end;
// use name and number as needed...
}
【讨论】：
你可以像这样使用正则表达式：
#include <iostream>
#include <string>
#include <regex>
#include <vector>
// create a struct to group your data
// this makes it easy to store it in a vector.
struct person_t
{
std::string name;
std::string number;
};
// overloaded output operator for printing one person's details
std::ostream& operator<<(std::ostream& os, const person_t& person)
{
std::cout << person.name << ": " << person.number << std::endl;
return os;
}
// get a vector of person_t based on the input
auto get_persons(const std::string& input)
{
// make a regex in this case a regex that will match one or more capital letters
// and groups them using the ()
// then match one or more digits and group them too.
static const std::regex rx{ "([A-Z]+)([0-9]+)" };
std::smatch match;
// a vector to hold all the persons
std::vector<person_t> persons;
// start at begin of string and look for first part of the string
// that matches the regex.
auto cbegin = input.cbegin();
while (std::regex_search(cbegin, input.cend(), match, rx))
{
// match[0] will contain the whole match,
// match[1]-match[n] will contain the groups from the regular expressions
// match[1] will contain the match with characters and thus the name
// match[2] will contain the match with the numbers and thus the number.
// create a person_t struct with this info
person_t person{ match[1], match[2] };
// and add it to the vector
persons.push_back(person);
cbegin = match.suffix().first;
}
return persons;
}
int main()
{
// parse and split the string
auto persons = get_persons("JACK1940383DAVID30284HAROLD68372TROY4392");
// show the output
for (const auto& person : persons)
{
std::cout << person;
}
}
【讨论】：
'\n' over std::endl。后者等同于前者，但会强制刷新输出，这通常是不需要的，并且可能会损害性能。
正如您可以使用的其他好的答案所指出的那样
find_first_of()、find_first_not_of() 和 substr() 来自 std::string 循环中regex但这可能太多了。我将添加 3 个您可能会发现的示例 更简单。
为了方便（我的）这里，前 2 个程序需要命令行上的文件名，测试文件是 in.txt。内容跟贴出来的一样
JACK1940383DAVID30284HAROLD68372TROY4392
最后一个例子只是解析声明为char[]的字符串数据
fscanf()
由于目标是使用格式化数据，fscanf() 是一个选项。由于数据结构很简单，所以程序就是一行循环：
char mask[] = "%50[^0-9]%50[0-9]";
while ( 2 == fscanf(F, mask, tk_key, tk_value))
std::cout << tk_key << "/" << tk_value << "\n";
所有示例的输出都相同
JACK/1940383
DAVID/30284
HAROLD/68372
TROY/4392
#include <errno.h>
#include <iostream>
int main(int argc,char** argv)
{
if (argc < 2)
{ std::cerr << "Use: pgm FileName\n";
return -1;
}
FILE* F = fopen(argv[1], "r");
if (F == NULL)
{
perror("Could not open file");
return -1;
}
std::cerr << "File: \"" << argv[1] << "\"\n";
char tk_key[50], tk_value[50];
char mask[] = "%50[^0-9]%50[0-9]";
while ( 2 == fscanf(F, mask, tk_key, tk_value))
std::cout << tk_key << "/" << tk_value << "\n";
fclose(F);
return 0;
}
只有 2 个状态，所以它不是一个花哨的 FSA ;) 状态机很适合表示这种东西，尽管在这里这似乎有点过头了。
#define S_LETTER 0
#define S_DIGIT 1
#include <algorithm>
#include <iostream>
#include <fstream>
using iich = std::istream_iterator<char>;
int main(int argc,char** argv)
{
std::ifstream in_file{argv[1]};
if ( not in_file.good()) return -1;
iich p {in_file}, eofile{};
std::string token{}; // string to build values
char st = S_LETTER; // state value for FSA
std::for_each(p, eofile,
[&token,&st](char ch)
{
char temp = 0;
switch (st)
{
case S_LETTER:
if ((ch >= '0') && (ch <= '9'))
{
std::cout << token << "/";
token = ch;
st = S_DIGIT; // now in number
}
else token += ch; // concat in string
break;
case S_DIGIT:
default:
if ((ch < '0') || (ch > '9'))
{ // is a letter
std::cout << token << "\n";
token = ch;
st = S_LETTER; // now in name
}
else token += ch; // concat in string
break;
}; // switch()
});
std::cout << token << "\n"; // print last token
}
这里我们没有循环。 for_each 从迭代器中获取数据并将其传递给一个函数，该函数将名称和值构建为字符串和couts
输出是一样的
#define S_LETTER 0
#define S_DIGIT 1
#include <iostream>
int main(void)
{
char one[] = "JACK1940383DAVID30284HAROLD68372TROY4392";
char* p = (char*)&one;
char* token = p;
char st = S_LETTER;
char temp = 0;
while (*p != 0)
{
switch (st)
{
case S_LETTER:
if ((*p >= '0') && (*p <= '9'))
{
temp = *p;
*p = 0;
std::cout << token << "/";
*p = temp;
token = p;
st = S_DIGIT; // now in number
}
break;
case S_DIGIT:
default:
if ( (*p < '0') || (*p > '9'))
{ // letter
temp = *p;
*p = 0;
std::cout << token << "\n";
*p = temp;
token = p;
st = S_LETTER; // now in name
}
break;
}; // switch()
p += 1; // next symbol
}; // while()
std::cout << token << "\n"; // print last token
}
这段代码只是使用了一个 C 风格的循环来解析输入数据
【讨论】：