挑战最短

#include<iostream>
int main(){int n,i,j,k;std::cin>>n;for(i=1;i<2*n;++i){k=i<=n?i:2*n-i;for(j=1;j<=n-k;++j)std::cout<<' ';std::cout<<'*';if(k>1){for(j=1;j<=2*k-3;++j)std::cout<<' ';std::cout<<'*';}std::cout<<'\n';}return 0;}

哈哈哈