How do I extract all the numbers in a string where the numbers are interspersed with letters? - c++

Question

How do I loop through a string consisting of numbers and letters and add only numbers to the vector?
For example if the input is:
e385p336J434Y26C2Z6X5Z2
I want to get a vector of int like this:
number = {385, 336, 434, 26, 2, 6, 5, 2}
The best I got was to iterate over the line and add all the digits like that:
#include <bits/stdc++.h>
int main(){
string f = "e385p336J434Y26C2Z6X5Z2";
vector<int> f_numb;
string sum;
for (int i = 0; i < f.size(); ++i){
if (('0' <= f[i]) && (f[i] <= '9')){
sum += (f[i]);
}
}
//std::cout << sum << std::endl;
vector<int> m_numb;
for (int i = 0; i < sum.size(); ++i){
m_numb.push_back(sum[i] - '0');
}
int sm;
for (int i = 0; i < m_numb.size(); ++i){
sm += m_numb[i];
std::cout << m_numb[i] << " ";
}
std::cout << std::endl;
}

Answer 1

Foregoing the unstated reason you're not using std::isdigit, you can/should simply build each number as you process its digits. Note that the code below does NOT check, nor care, about unsigned overflow, and makes no attempt at processing negative numbers.
#include <iostream>
#include <string>
#include <vector>
int main()
{
std::string f = "e385p336J434Y26C2Z6X5Z2";
std::vector<unsigned int> f_numb;
for (auto it = f.begin(); it != f.end();)
{
if ('0' <= *it && *it <= '9')
{
unsigned int sm = 0;
for (;it != f.end() && '0' <= *it && *it <= '9'; ++it)
sm = (sm * 10) + (*it - '0');
f_numb.emplace_back(sm);
}
else
{
++it;
}
}
for (auto x : f_numb)
std::cout << x << ' ';
std::cout << '\n';
}
Output
385 336 434 26 2 6 5 2
That, assuming I understand your question vs. your code, which differ highly in their apparent goals.

Answer 2

Another aproach making more use of standard library functions.
Live demo here : https://onlinegdb.com/8eEgREuEN
I tend to make functions of substeps so I can test them individually
#include <algorithm>
#include <iterator> // back_inserter
#include <string>
#include <vector>
#include <iostream>
#include <string_view>
// I like to make functions for substeps (they tend to be reusable)
std::vector<std::string> get_number_substrings(const std::string& input)
{
static const std::string_view digits{ "0123456789" };
std::vector<std::string> substrings;
auto start_pos = input.find_first_of(digits, 0ul);
auto end_pos = start_pos;
auto max_length = input.length();
while (start_pos < max_length)
{
end_pos = std::min(max_length, input.find_first_not_of(digits, start_pos));
if (end_pos != start_pos)
{
substrings.emplace_back(&input[start_pos], end_pos - start_pos);
start_pos = input.find_first_of(digits, end_pos);
}
}
return substrings;
}
std::vector<int> get_numbers(const std::string& input)
{
auto numbers = get_number_substrings(input);
std::vector<int> output;
// now transform the string to vector<int>
// the back_inserter is needed because output doesn't have allocated memory yet
// and that needs to be build up during the transform.
// https://en.cppreference.com/w/cpp/iterator/back_inserter
// https://en.cppreference.com/w/cpp/algorithm/transform
std::transform(numbers.begin(), numbers.end(), std::back_inserter(output), [](const std::string& string)
{
return std::stoi(string);
});
return output;
}
int main()
{
std::string input{ "e385p336J434Y26C2Z6X5Z2" };
auto output = get_numbers(input); // output will be a std::vector<int>
// Use range based for loop
// https://en.cppreference.com/w/cpp/language/range-for
bool comma = false;
for (const int value : output)
{
if (comma) std::cout << ", ";
std::cout << value;
comma = true;
}
return 0;
}

Answer 3

Will this work for you?
std::string f = "e385p336J434Y26C2Z6X5Z2";
std::vector<int> f_numb;
std::string sum;
#define MAX_DIGITS 25
char aBuildNumber[MAX_DIGITS];
int aBuildCount=0;
std::vector<int> m_numb;
for (int i = 0; i < f.size(); ++i)
{
if (!isdigit(f[i]) || aBuildCount>=MAX_DIGITS-1)
{
if (aBuildCount>0) m_numb.push_back(atoi(aBuildNumber));
aBuildCount=0;
}
else {aBuildNumber[aBuildCount++]=f[i];aBuildNumber[aBuildCount]=0;}
}
if (aBuildCount>0) m_numb.push_back(atoi(aBuildNumber));
int sm=0;
for (int i = 0; i < m_numb.size(); ++i)
{
sm += m_numb[i];
std::cout << m_numb[i] << " ";
}
std::cout << std::endl;