storing extracted characters in a vector of strings - c++

Question

I should reasonably be able to store chars in a std::vector of strings, if the conversion is considered.
Here is the try:
vector<string> f (vector<string> input)
{
vector<string> output;
for (int i=0; i<input.size(); i++) // vector iteration
{
for (int j=0;j<input[i].size(); j++) // string iteration
{
output.push_back(string(input[i].at(j))); // access to characters
}
}
return output;
}
input[i] is a string, and input[i].at(j) is a char; thus, I've converted it to string before pushing to vector<string>.
I'm wondering what's wrong with this approach. Especially, the compiler's error is undecipherable to me:
invalid conversion from '__gnu_cxx::__alloc_traits<std::allocator<char> >::value_type {aka char}' to 'const char*' [-fpermissive]
Edit:
f must work as follows.
Suppose there are 3 strings in the input vector: {abcd,efdr,loab}; then, the output shall extract all atormic characters like: {abcdefdrloab}

Answer 1

To correct your error change
output.push_back(string(&input[i].at(j)));
from
output.push_back(string(input[i].at(j)));
Basically
**for (int i=0; i<input.size(); i++) \\vector iteration**
This is a wrong way of iteration .For containers iterators should be used for iterating
Below copies string from one vector (Use of iterator and stl you can use copy_if or lambda)
#include <iostream>
#include <iterator>
#include<vector>
#include<string>
#include<algorithm>
using namespace std;
vector<string> f (vector<string> input)
{
vector<string> output;
copy(input.begin(),input.end(),back_inserter(output));
return output;
}
int main()
{
vector<string> h{"hello"},x;
x=f(h);
copy(x.begin(),x.end(),ostream_iterator<string>(cout," "));
}
Output
hello Program ended with exit code: 0
But to answer you question and fix of your Code
Below is the modified code
#include <iostream>
#include <iterator>
#include<vector>
#include<string>
#include<algorithm>
using namespace std;
vector<string> f (vector<string> input)
{
vector<string> output;
for (int i=0; i<input.size(); i++)
{
for (int j=0;j<input[i].size(); j++)
{
output.push_back(string(&input[i].at(j)));
}
}
return output;
}
vector<string> fi (vector<string> input)
{
vector<string> output;
copy(input.begin(),input.end(),back_inserter(output));
return output;
}
int main()
{
vector<string> h{"hello"},x,y;
x=fi(h);
y=f(h);
copy(x.begin(),x.end(),ostream_iterator<string>(cout," "));
copy(y.begin(),y.end(),ostream_iterator<string>(cout," "));
}
Output
hello hello ello llo lo o Program ended with exit code: 0
Solution after the edit
#include <iostream>
#include <iterator>
#include<vector>
#include<string>
#include<algorithm>
#include <numeric>
using namespace std;
template<typename T, typename... Args>
void push_back_vec(std::vector<T>& v, Args&&... args)
{
(v.push_back(args), ...);
}
int main()
{
vector<string>x;
push_back_vec(x, "abc", "cds", "ma");
string a = accumulate(x.begin(), x.end(), string(""));
cout<<a;
}
Output
abccdsmaProgram ended with exit code: 0
More easier format
#include <iostream>
#include <iterator>
#include<vector>
#include<string>
#include<algorithm>
#include <numeric>
using namespace std;
int main()
{
vector<string>x{"abc", "cds", "ma"},a;
a.push_back(accumulate(x.begin(), x.end(), string("")));
copy(a.begin(),a.end(),ostream_iterator<string>(cout," "));
}

Answer 2

try this string(1, input[i].at(j))