practice_4.cpp

#include <iostream>
using namespace std;

int main() {
    int n,i,j,nj,l;
    bool flip;
    cin>>n;
    for(i=0,l=n;i<n;i++,l--){
        for(j=0,nj=0,flip = true;nj<(2*n)-1;nj++,j-=(1-(2*flip)),flip=((j<n-1)&&flip))
            cout<<((j<l)?(char)(j+49):' ');
        cout<<endl;
    }
    return 0;
}