Spiral Hourglass of Numbers
This program prints an hourglass filled with numbers in spiral order.
Problem Statement
Write a Java program that prints an hourglass of numbers arranged in spiral order with 7 rows.
Source Code
| 1 | public class SpiralHourglassNumbers { |
| 2 | public static void main(String[] args) { |
| 3 | int n = 7; |
| 4 | int[][] arr = new int[n][n]; |
| 5 | int top=0, left=0, bottom=n-1, right=n-1, num=1; |
| 6 | while(top<=bottom && left<=right) { |
| 7 | for(int i=left; i<=right; i++) arr[top][i]=num++; |
| 8 | top++; |
| 9 | for(int i=top; i<=bottom; i++) arr[i][right]=num++; |
| 10 | right--; |
| 11 | for(int i=right; i>=left; i--) arr[bottom][i]=num++; |
| 12 | bottom--; |
| 13 | for(int i=bottom; i>=top; i--) arr[i][left]=num++; |
| 14 | left++; |
| 15 | } |
| 16 | for(int i=0; i<n; i++) { |
| 17 | for(int j=0; j<n; j++) { |
| 18 | if(i<=j && i+j>=n-1) System.out.print(arr[i][j] + "\t"); |
| 19 | else System.out.print(" \t"); |
| 20 | } |
| 21 | System.out.println(); |
| 22 | } |
| 23 | } |
| 24 | } |
Program Output
1 2 3 4 5 6 7
20 21 22 23 24 25
19 32 33 34 35 26
18 31 36 37 38 27
17 30 29 28
16 15 14
13
Explanation
A full square spiral matrix of numbers is built first, and then a printing condition (i<=j && i+j>=n-1) selectively shows only the cells forming an hourglass shape, hiding the rest with blanks.