https://www.acmicpc.net/problem/10992
#include <iostream>
using namespace std;
int main() {
int n;
cin>>n;
for(int i=1;i<n;i++){
for(int j=n-i;j>0;j--) cout<<" ";
cout<<"*";
for(int j=0;j<(i-2)*2+1;j++) cout<<" ";
if(i!=1) cout<<"*";
cout<<"\n";
}
for(int i=0;i<(n-1)*2+1;i++) cout<<"*";
}