题解

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