```#include <iostream>
using namespace std;

int main()
{
int *A,n,x, ch;
int i,j;

cout << "Enter dimension : " ;
cin >> n;

A = new int[n];

do
{
cout << "\n\n---Diagonal matrix---" << endl;
cout << "1. Create " << endl;
cout << "2. Get " << endl;
cout << "3. Set " << endl;
cout << "4. Display " << endl;
cout << "5. Exit " << endl;
cout << "Enter your choice : ";
cin >> ch;

switch(ch)
{
case 1 :
cout << "Enter the diagonal elements : \n";
for (int i=1; i<=n; i++)
cin >> A[i-1];
break;

case 2 :
cout << "Enter indices : ";
cin >> i >> j;
if (i==j)
cout << "Element is : " << A[i-1] << endl;
else
cout << "Element is : 0 " << endl;
break;

case 3 :
cout << "Enter the element : ";
cin >> x;
cout << "Enter the indices : ";
cin >> i >> j;
if (i==j)
{
A[i-1] = x;
cout << "Element is inserted "<< endl;
}
else
cout << "Element cannot be inserted at those indices!" << endl;
break;

case 4 :
for (int i=1; i<=n; i++)
{
for(int j=1; j<=n; j++)
{
if (i==j)
cout << A[i-1] << " ";
else
cout << "0 ";
}
cout << endl;
}
break;

}

}
while(ch != 5);

return 0;
}```