题目:

//while循环实现int main()
{int n;cout << "请输入边长：";cin >> n;int i = 1; while (i <= n){ // 控制行数int j = 1;while (j <= n){ // 控制列数if (i == 1 || i == n || j == 1 || j == n){cout << "*";}else{cout << " ";}j++;}cout << endl;i++;}return 0;
}

//for循环实现（更简单）#include <iostream>
using namespace std;int main()
{int n;cout << "请输入边长：";cin >> n;for(int i=1;i<=n;i++){for(int j=1;j<=n;j++){if (i == 1 || i == n || j == 1 || j == n){cout << "*";}else{cout << " ";}}cout<<endl;}return 0;
}