increasing size of array of string in c++ - c++

Question

I want to increase the size of the array of string after declaring it once, how can it be done. I need to increase the size in the following code..
#include<iostream>
using namespace std;
#include<string>
int main()
{
int n;
string A[] =
{ "vaibhav", "vinayak", "alok", "aman" };
int a = sizeof(A) / sizeof(A[0]);
cout << "The size is " << a << endl;
for (int i = 0; i < a; i++)
{
cout << A[i] << endl;
}
cout << "Enter the number of elements you want to add to the string"
<< endl;
cin >> n;
cout << "ok now enter the strings" << endl;
for (int i = a; i < n + a; i++)
{
cin >> A[i];
}
a = a + n;
A.resize(a); // THIS KIND OF THING
for (int i = 0; i < a; i++)
{
cout << A[i] << endl;
}
return 0;
}

Answer 1

Plain and simple: you cannot.
You can get a larger array, copy all your stuff over and use that instead. But why do all that, when there is a perfectly good class already there, doing it all for you: std::vector.
#include <iostream>
#include <string>
#include <vector>
int main()
{
std::vector<std::string> A = {"vaibhav", "vinayak", "alok", "aman"};
std::cout << "The size is " << A.size() << std::endl;
for(string s : A)
{
std::cout << s << std::endl;
}
// want to enter more?
sd::string more;
std::cin >> more;
A.push_back(more);
std::cout << "The size is " << A.size() << std::endl;
for(string s : A)
{
std::cout << s << std::endl;
}
return 0;
}

Answer 2

Convert your code over to use std::vector and this problem becomes much easier to solve.
#include<iostream>
#include<string>
#include<vector>
int main(){
int n;
std::vector<std::string> A = {"vaibhav", "vinayak", "alok", "aman"};
int a = A.size();
std::cout << "The size is " << a << std::endl;
//Prefer Range-For when just iterating over all elements
for(std::string const& str : A){
std::cout << str << std::endl;
}
std::cout << "Enter the number of elements you want to add to the string" << std::endl;
std::cin >> n;
std::cout << "ok now enter the strings" << std::endl;
for(int i = 0; i < n; i++ ) {
//emplace_back automatically resizes the container when called.
A.emplace_back();
std::cin >> A.back();
//If you're using C++17, you can replace those two lines with just this:
//std::cin >> A.emplace_back();
}
for(std::string const& str : A){
std::cout << str << std::endl;
}
return 0;
}
Also, don't use using namespace std;, since it leads to expensive to fix bugs and makes your code harder to read for other C++ programmers.

Answer 3

I want to increase the size of the array of string after declaring it
once, how can it be done.
It cannot be done. Use std::vector if the element count isn't known at compile time or can change dynamically. It even has a resize member function named exactly like the one in your code.

Answer 4

You cannot increase the size of a Raw Array, you could use an std::vecto<std::string> as this type of array can grow at runtime.
However, you could also create a class that will store an array of string and create your own implementation to resize the raw array. Which would be creating a bigger array and copying all the other values over, then setting the class array to the new array (or just return it)