#include <iostream>
using namespace std;
int main()
{
    int n;
    cin >> n;
    for(int i=1;i<=n;i++)
    {
        cout << " ";
        for(int j=1;j<=n;j++)
        {
            cout << " ";
            if(i+j==n+1)
            {
                cout << 1 << " ";
            }
            else
            {
                cout << 0 << " ";
            }
        }
        cout << endl;
    }
}

把上一题的循环变量改一下就行了

#include <iostream>
using namespace std;
int main()
{
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n; j++)
        {
            cout << "  ";
            if (i == j)
            {
                cout << 1;
            }
            else
            {
                cout << 0;
            }
            if (j == n)
            {
                cout << endl;
            }
        }
    }
    return 0;
}