box_pattern.c

#include <stdio.h>

// Get Minimum Function
int min(int a, int b){
  if(a < b){
    return a;
  }
  return b;
}

int main(){
  int i, j; // Iterators
  int i0;
  int limit, limit_in;
  int N = 5; // Box Size Param

  for(i = 0; i < 2 * N - 1; i++){
    if(i >= N){
      i0 = 2 * (N - 1) - i;
    } else {
      i0 = i;
    }
    limit = 2 * N - 2 - i0;

    for(j = 0; j < 2 * N - 1; j++){
      printf(" ");
      if(j > 0){
        if(j <= limit){
          printf("%d", N - min(i0, j));
          limit_in = N - min(i0, j);

        } else {
          printf("%d", limit_in + 1);
          limit_in = limit_in + 1;

        }
      } else {
        printf("%d", N);
      }
    }
    printf("\n");
  }
  return 0;
}

/*
For N = 5
Prints:
 5 5 5 5 5 5 5 5 5
 5 4 4 4 4 4 4 4 5
 5 4 3 3 3 3 3 4 5
 5 4 3 2 2 2 3 4 5
 5 4 3 2 1 2 3 4 5
 5 4 3 2 2 2 3 4 5
 5 4 3 3 3 3 3 4 5
 5 4 4 4 4 4 4 4 5
 5 5 5 5 5 5 5 5 5
 */