construirea matrice

//se contruieste o matrice patratica

#include <iostream>

using namespace std;

int main()
{
    int a[100][100],m,i,j,nr;
    cout<<"m= ";cin>>m;
    for (j=1;j<=m;j++)
    {
     if (j%2==1)
    for (i=1;i<=m;i++)
    {
        a[i][j]=nr;
        nr++;
    }
    else
    for (i=m;i>=1;i--)
    {
        a[i][j]=nr;
        nr++;
    }
    }
    for (i=1;i<=m;i++)
    {
        for (j=1;j<=m;j++)
        cout<<a[i][j]<<" ";
        cout<<'\n';
    }
    return 0;
}