在 C++ 中拆分没有空格的字符串

Question

I have the a string which consists of key value pairs but no delimiter character:

A0X3Y21.0

All values may be floats. How can I split this string up into:

A = 0, X = 3, Y = 21.0

My current method was to use strtof() which works generally except for one annoying case where an 0 is before an X and so the above string is instead split into:

A = 0x3, Y = 21.0

Answer 1

For parsing, normally I use std::stringstream s, defined in the header <sstream> . An example use here:

#include <sstream>
#include <string>
#include <iostream>

int main() {
    std::stringstream parser("A0X3Y21.0");
    std::stringstream output;
    char letter;
    double value;
    while (parser>>letter&&parser>>value) {
        output << letter;
        output << " = ";
        output << value;
        output << " ";
    }
    std::cout<<output.str();
}

This would output this:

A = 0 X = 3 Y = 21

Answer 2

Assuming you just have to print these, you don't even have to use strtof , you just have to find the beginning and end of the float string. Here's a function that demonstrates this (this function assumes that the length of the variable names in the string are only one character since from your example, but it isn't too hard to fix that if need be):

#include <iostream>
#include <string>
#include <string_view>

void foo(const std::string_view str)
{
    for (size_t i = 0; i < str.size(); ++i)
    {
        std::cout << str[i] << " = ";
        size_t float_end_pos = str.find_first_not_of("1234567890.", i + 1) - 1;
        std::string_view float_str = str.substr(i + 1, float_end_pos - i);
        std::cout << float_str << '\n';
        i = float_end_pos;
    }
}

int main()
{
    foo("A0X3Y21.0");
}

Output:

A = 0
X = 3
Y = 21.0

And it shouldn't be too hard to adapt the basic premise of this to whatever you need to do.