#89 B

The rule is simple. First determin the number of rows to print, then for every row follow the rule.

Total rows = 2n + 1. 

The ith row has 2i + 1 digits to print, from 0 to i then to 0.

The ith row skip 2n - 2i spaces.

Accepted.

#include <stdio.h>
#include <string.h>

int main() {
        int n;
        scanf("%d", &n);

        int i,j,k;
        for( i=0;i<n;i++ ) {
                k = 2*n - 2*i;
                for( j=0;j<k;j++ ) 
                        printf(" ");
                k = 2*i + 1;
                for( j=0;j<i;j++ ) 
                        printf("%d ", j);
                for( ;j>0;j-- ) 
                        printf("%d ", j);
                printf("%d\n",j);
        }

        for( ;i>=0;i-- ) {
                k = 2*n - 2*i;
                for( j=0;j<k;j++ ) 
                        printf(" ");
                k = 2*i + 1;
                for( j=0;j<i;j++ ) 
                        printf("%d ", j);
                for( ;j>0;j-- ) 
                        printf("%d ", j);
                printf("%d\n",j);
        }

        return 0;
}