diamond_number.cpp

#include<stdio.h>
#define print_diamonds for(int j=0; j<n+x; j++) printf(j<n-x-1?" ":"%d", j<n-1?x-(n-j)+2:n-j+x); printf("\n")
int main() {
    int n; scanf("%d", &n);
    for(int i=0, x=0; i<n; i++, x++){print_diamonds;}
    for(int i=1, x=n-2; i<n; i++, x--){print_diamonds;}
    return 0;
}

/*
Input:
9

Output:
        1
       121
      12321
     1234321
    123454321
   12345654321
  1234567654321
 123456787654321
12345678987654321
 123456787654321
  1234567654321
   12345654321
    123454321
     1234321
      12321
       121
        1
*/