#include <iostream>
#include <vector>
#include <sstream>
#include <iomanip>  // for setw, setfill
 
using namespace std;
 
int binary(int number);
std::string binStr(unsigned int exponent, unsigned int size);
 
int main()
{
 
    vector<vector<int> > matrix;
 
    cout<<"Please enter the size of the identity matrix"<<endl;
    int n;
    cin>>n;
 
// Initialize the matrix
    matrix.resize(n);
    for (int i=0; i<n;i++)
        matrix[i].resize(n);
 
// Fill the matrix
    for (int col = 0; col<n; col++)
    {
        std::string bin = binStr(n-col,n);
        for (int row=0; row<n; row++)
            matrix[col][row] = bin[row]-'0';
    }
 
 
// Print the matrix and return
    for(unsigned int y = 0; y < n; y++)
    {
        for(unsigned int x = 0; x < n; x++)
            cout << "\t" << matrix[y][x];
        cout << "\n";
    }
    return 0;
}
 
std::string binStr(unsigned int exponent, unsigned int size)
{
    // You do not need a string stream (which is like using a bazooka to kill a fly...)
    // Instead, just create a string of the required length
    // 'str' will contain the binary representation of 2^exponent
    std::string str(size,'0');
    if(exponent <= size && exponent > 0)
        str[size - exponent] = '1';
    return str;
}

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