Extracting integers from a string which has no space - c++

Question

so i'm currently trying to extract integers from a string. This is what i've done so far
#include <iostream>
#include <string>
#include <vector>
#include <sstream>
using namespace std;
int main() {
string s="VA 12 RC13 PO 44";
stringstream iss;
iss << s;
string temp;
vector<int> a1;
int j;
while (!iss.eof()) {
iss >> temp;
if (stringstream(temp)>>j) {
a1.push_back(j);
}
temp="";
}
}
Now, this works fine, but if i change the string to something like s="VA12RC13PO44", aka with no spaces this code doesn't work. Does anyone know how to go about solving this?
Thanks

Answer 1

There are really many many possible solutions. It depends on how advanced you are. Personally I would always use a std::regex approach for such tasks, but this is maybe too complicated.
A simple handcrafted solution could be this:
#include <iostream>
#include <string>
#include <vector>
#include <cctype>
int main() {
std::string s = "VA 12 RC13 PO 44";
std::vector<int> a;
// We want to iterate over all characters in the string
for (size_t i = 0; i < s.size();) {
// Basically, we want to continue with the next character in the next loop run
size_t increments{1};
// If the current character is a digit, then we convert this and the following characters to an int
if (std::isdigit(s[i])) {
// The stoi function will inform us, how many characters ahve been converted.
a.emplace_back(std::stoi(s.substr(i), &increments));
}
// Either +1 or plus the number of converted characters
i += increments;
}
return 0;
}
So, here we check character for character of the string. If we find a digit, then we build a substring of the string, starting at the current character position and hand it of to std::stoi for conversion.
std::stoi will convert all characters it can get an convert it to an int. If there is a non-digit character, it stops conversion and informs on how many characters have been converted. We add this value to the current position of the evaluated character, to avoid to convert the digits from the same integer substring over and over again.
At the end, we put the resulting integer into the vector. We use emplace_back to avoid unnecessary temporary value.
This will of course work with or without blanks.