要是不写函数就太麻烦、太乱了，还是用函数好一点~

已AC，请放心食用

#include <iostream>
using namespace std;
void squ(int n)
{
    for (int i = 1; i <= n; i++)
    {
        cout << "*";
    }
    cout << endl;
}
void are(int n)
{
    for (int i = 1; i <= n - 2; i++)
    {
        cout << "*";
        for (int j = 1; j <= n - 2; j++)
        {
            cout << " ";
        }
        cout << "*" << endl;
    }
}
int main()
{
    int n;
    cin >> n;
    squ(n);
    are(n);
    squ(n);
    return 0;
}

养成好习惯，看后点个赞😎！

AC Code

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++)
        cout << "*";
    cout << endl;
    for (int i = 1; i <= n - 2; i++)
    {
        for (int j = 1; j <= n; j++)
        {
            if (j == 1 || j == n)
                cout << "*";
            else
                cout << " ";
        }
        cout << endl;
    }
    for (int i = 1; i <= n; i++)
        cout << "*";
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int n;
int main()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n; j++)
        {
            if (i == 1 || i == n)
            {
                cout << "*";
            }
            else
            {
                if (j == 1 || j == n)
                {
                    cout << "*";
                }
                else
                {
                    cout << " ";
                }
            }
        }
        cout << endl;
    }
    return 0;
}

#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++) { if (i != 1 and i != n) { if (j != 1 and j != n) { cout << " "; } else { cout << ""; } } else { cout << ""; } } cout << endl; } return 0; } //只有50分啊

#include <iostream>
using namespace std;
int main(){
    int k,net=1,x=0,sum=0;
    cin>>k;
    for(int i=1;i<=k;i++){
        sum+=net,x++;
        if(x==net)net++,x=0;
    }
    cout<<sum<<endl;
    return 0;
}