How to add integers and strings in the same vector? - c++

Question

I need help for my university homework. i'm still new to this.
Basically i am doing a run-length encoding and i don't know how to add the letter after the counter:
#include <iostream>
#include <string>
#include <vector>
#include <stdexcept>
void error(std::string str)
{
throw std::runtime_error(str);
}
int main()
{ int counter = 1;
std::string id;
std::vector<int> v;
std::cout << "Enter the data to be compressed: ";
std::cin >> id;
try
{ for(int i = 0; i < id.size(); i++)
{
if(std::isdigit(id[i]))
error("invalid input");
}
std::cout << "The compressed data is: ";
for(int i = 0; i < id.size(); i++)
{
if(id[i] == id[i+1])
{
counter++;
}
else if(id[i]!= id[i+1])
{
v.push_back(counter);
v.push_back(id[i]);
counter=1;
}
}
for(int j = 0; j < v.size(); j++)
std::cout << v[j];
}
catch(std::runtime_error& str)
{
std::cerr << "error: " << str.what() << std::endl;
return 1;
}
return 0;
}
For example if i input aaabbb, the probram should output 3a3b. The problem is that it outputs 397398 97 and 98 being the ascii code for a and b.
i don't know how to put the letter after the counter and for them to be in the same vector.

Answer 1

If you want to serialize as a string try this :
#include <iostream>
#include <string>
#include <vector>
#include <stdexcept>
#include <sstream>
void error(std::string str) {
throw std::runtime_error(str);
}
int main() {
std::ostringstream stream;
int counter = 1;
std::string id;
std::cout << "Enter the data to be compressed: ";
std::cin >> id;
try {
for (int i = 0; i < id.size(); i++) {
if (std::isdigit(id[i]))
error("invalid input");
}
std::cout << "The compressed data is: ";
for (int i = 0; i < id.size(); i++) {
if (id[i] == id[i + 1]) {
counter++;
} else if (id[i] != id[i + 1]) {
stream << counter;
stream << (char) id[i];
counter = 1;
}
}
std::cout << stream.str() << std::endl;
} catch (std::runtime_error& str) {
std::cerr << "error: " << str.what() << std::endl;
return 1;
}
}

Answer 2

v[j] from std::cout << v[j] is of type int and that is why std::cout writes a number. To write it as a character, you should cast v[j] to char as follows: std::cout << (char)v[j]. In this way, std::cout will use the char specialization, not the int one.

Answer 3

While the other answers might give you the output you need, I believe the idiomatic way to solve this is using a class to hold both the character and its count. There are two obvious choices.
std::pair
Could also be std::tuple if you prefer it for consistency or whatever reason. Save your results in a std::vector<std::pair<char, int>. This saves the information, but to print it you would need to define an appropriate function. Add elements via
v.emplace_back(character, count);
Wrapper Class
If you want to offer some functionality without outside helper classes, define a custom wrapper class such as the following.
class CharacterCount {
private:
char character;
int count;
public:
CharacterCount(char character, int count):
character(character), count(count) {}
explicit operator std::string() const { return std::to_string(count) + character;
// Other helper functions or constructors you require
}
This simplifies printing
for (auto& character_count : v)
std::cout << static_cast<std::string>(character_count);
I believe because std::ostream::operator<< is templated, you cannot get an implicit conversion to std::string to work. I would advise against implicit conversion anyway.
You can use the same emplace_back syntax as before because we offer an appropriate constructor.

Answer 4

So you take your input in a string and ultimately just need to stream this information out, ultimately meaning there's really no reason to store the information in a vector, just output it! You can use find_if with a lambda to find the non-consecutive character (or find_if_not if you prefer.)
for(string::const_iterator finish, start = cbegin(id); start != cend(id); start = finish) {
finish = find_if(start, cend(id), [value = *start](const auto i) { return i != value; } );
cout << distance(start, finish) << *start;
}
Live Example