#include <stdio.h>
struct Matrix
{
  int A[10];
  int n;
};
void Set(struct Matrix *m,int i,int j,int x)
{
  if(i==j)
    m->A[i-1]=x;

}
int Get(struct Matrix m,int i,int j)
{
  if(i==j)
    return m.A[i-1];
  else
    return 0;
}
void Display(struct Matrix m)
{
  int i,j;
  for(i=0;i<m.n;i++)
  {
    for(j=0;j<m.n;j++)
    {
      if(i==j)
        printf("%d ",m.A[i]);
      else
        printf("0 ");
    }
    printf("\n");
 }
}
int main()
{
  struct Matrix m;
  m.n=4;

  Set(&m,1,1,5);Set(&m,2,2,8);Set(&m,3,3,9);Set(&m,4,4,12);
  printf("%d \n",Get(m,2,2));
  Display(m);
  return 0;
}

class Diagonal
{
private:
  int n;
  int * A;
public:
  Diagonal(int n)
  {
    this->n;
    A= new int[n];
  }
  void set(int i, int j, int x);
  int get(int i, intj);
  void Display()
  ~Diagonal();
};
void Diagonal::Set(int i,int j,int x)
{
  if(i==j)
    A[i-1]=x;
}
int Diagonal::Get(int i,int j)
{
  if(i==j)
    return A[i-1];
  return 0;
}
void Diagonal::Display()
{
  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;
 }
}
int main()
{
  int d;
  cout<<"Enter Dimensions";
  cin>>d;

  Diagonal dm(d);
  int x;
  cout<<"enter All elements";
  for(int i=1;i<=d;i++)
  {
    for(int j=1;j<=d;j++)
    {
      cin>>x;
      dm.Set(i,j,x);
    }
  }
  dm.Display();
  return 0;
}

struct Matrix
{
  int * A;
  int n;
};

void Set(struct Matrix *m,int i,int j,int x)
{
  if(i>=j)
    m->A[m->n*(j-1)+(j-2)* (j-1)/2+i-j]=x;
}
int Get(struct Matrix m,int i,int j)
{
  if(i>=j)
    return m.A[m.n*(j-1)+(j-2)* (j-1)/2+i-j];
  else
    return 0;
}
void Display(struct Matrix m)
{
  int i,j;
  for(i=1;i<=m.n;i++)
  {
    for(j=1;j<=m.n;j++)
    {
      if(i>=j)
        printf("%d ",m.A[m.n*(j-1)+(j-2)* (j-1)/2+i-j]);
      else
        printf("0");
    }
    printf("\n");
  }
}
int main()
{
  struct Matrix m;
  int i,j,x;
  printf("Enter Demension");
  scanf("%d \n",&m.n);
  m.A=(int *)malloc(m.n*(m.n+1)/2*sizeof(int));
  printf("enter all elements");
  for(i=1;i<=m.n;i++)
  {
    for(j=1;j<=m.n;j++)
    {
      scanf("%d\n", &x);
      Set(&m,i,j,x);
    }
  }
  printf("\n\n");
  Display(m);
  return 0;
}

#include <iostream>
using namespace std;

class LTMatrix{
private:
    int n;
    int* A;
public:
    LTMatrix(int n){
        this->n = n;
        A = new int [n * (n + 1)/2];
    }
    ~LTMatrix(){ delete[] A; }
    void Display(bool row=true);
    void setRowMajor(int i, int j, int x);
    void setColMajor(int i, int j, int x);
    int getRowMajor(int i, int j);
    int getColMajor(int i, int j);
    int getN(){ return n; }

};

void LTMatrix::setRowMajor(int i, int j, int x) {
    if (i >= j){
        int index = ((i * (i - 1))/2) + j - 1;
        A[index] = x;
    }
}

void LTMatrix::setColMajor(int i, int j, int x) {
    if (i >= j){
        int index = (n * (j-1) - (((j-2) * (j-1))/2)) + (i-j);
        A[index] = x;
    }
}

int LTMatrix::getRowMajor(int i, int j) {
    if (i >= j){
        int index = ((i * (i - 1))/2) + j - 1;
        return A[index];
    } else {
        return 0;
    }
}

int LTMatrix::getColMajor(int i, int j) {
    if (i >= j){
        int index = (n * (j-1) - (((j-2) * (j-1))/2)) + (i-j);
        return A[index];
    } else {
        return 0;
    }
}

void LTMatrix::Display(bool row) {
    for (int i=1; i<=n; i++){
        for (int j=1; j<=n; j++){
            if (i >= j){
                if (row){
                    cout << getRowMajor(i, j) << " ";
                } else {
                    cout << getColMajor(i, j) << " ";
                }
            } else {
                cout << 0 << " ";
            }
        }
        cout << endl;
    }
}

int main() {

    LTMatrix rm(4);
    rm.setRowMajor(1, 1, 1);
    rm.setRowMajor(2, 1, 2);
    rm.setRowMajor(2, 2, 3);
    rm.setRowMajor(3, 1, 4);
    rm.setRowMajor(3, 2, 5);
    rm.setRowMajor(3, 3, 6);
    rm.setRowMajor(4, 1, 7);
    rm.setRowMajor(4, 2, 8);
    rm.setRowMajor(4, 3, 9);
    rm.setRowMajor(4, 4, 10);

    rm.Display();
    cout << endl;

    LTMatrix cm(4);
    cm.setColMajor(1, 1, 1);
    cm.setColMajor(2, 1, 2);
    cm.setColMajor(2, 2, 3);
    cm.setColMajor(3, 1, 4);
    cm.setColMajor(3, 2, 5);
    cm.setColMajor(3, 3, 6);
    cm.setColMajor(4, 1, 7);
    cm.setColMajor(4, 2, 8);
    cm.setColMajor(4, 3, 9);
    cm.setColMajor(4, 4, 10);

    cm.Display(false);

    return 0;
}