C++ :

#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;
    
    // 输出上半部分
    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= n - i; ++j)
            cout << " ";
        for (int k = 1; k <= 2 * i - 1; ++k)
            cout << "*";
        cout << "\n";
    }
    
    // 输出下半部分
    for (int i = n - 1; i >= 1; --i) {
        for (int j = 1; j <= n - i; ++j)
            cout << " ";
        for (int k = 1; k <= 2 * i - 1; ++k)
            cout << "*";
        cout << "\n";
    }
    
    return 0;
}