Correct implementation of 2d vector population - c++

Question

I have a constructor and a method in an implementation file:
Boggle::Boggle(std::string boardString){
dim = sqrt(boardString.size());
vector<vector<char> > grid(dim, vector<char>(dim));
int co = 0;
for (int i = 0; i < dim; i++)
{
for (int j = 0; j < dim; j++)
{
grid[i][j] = boardString[co];
co++;
}
}
}
void Boggle::printMe() {
for (auto inner : grid)
{
for (auto item : inner)
{
cout << item << " ";
}
cout << endl;
}
}
The program executes, but doesn't do anything. As you can see I have sized my vector when I declared it. I believe the issue lies in my logic of assigning a character to a vector from a string perhaps.

Answer 1

As hinted in comments your vector grid is local to your function. You mostly likely wanted to use a class variable but ended up creating a local variable. You can use resize to set the dimensions of your grid. Also its better to ceil the sqrt to make sure that we are not missing any characters.
Example:
#include <stdio.h>
#include <vector>
#include <string>
#include <cmath>
#include <iostream>
using namespace std; // Avoid this
class Boggle{
public:
int dim;
vector<vector<char>> grid;
Boggle(string boardString);
void printMe();
};
Boggle::Boggle (std::string boardString)
{
dim = ceil(sqrt(boardString.size ()));
grid.resize(dim, vector <char>(dim));
int co = 0;
for (int i = 0; i < dim; i++) {
for (int j = 0; j < dim; j++)
{
grid[i][j] = boardString[co];
co++;
}
}
}
void Boggle::printMe ()
{
for (auto inner:grid) {
for (auto item:inner)
{
cout << item << " ";
}
cout << endl;
}
}
int main(){
Boggle boggle("hello world");
boggle.printMe();
return 0;
}
Result:
h e l l
o w o
r l d