知识点：

循环控制：

循环输出图形 

#include <iostream>
using namespace std;

int main() {
    int n;

    while (cin >> n) {
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n; j++) {
                if ((i == n) || (i == j) || (j == 1)) {
                    cout << "* ";
                } else {
                    cout << "  ";
                }
            }
            cout << endl;
        }
    }

    return 0;
}