Diamond Number-Star Pattern (Sandwich Inverted)

Understanding the Problem

The goal is to print a diamond-shaped pattern where numbers are printed in decreasing order in the upper half, followed by a repeated middle row, and then increasing order in the lower half. Each number is followed by a star except for the last number in each row.

Pattern Explanation

The pattern consists of three parts: the upper half, the repeated middle row, and the lower half.

6*6*6*6
5*5*5
4*4
3
3
4*4
5*5*5
6*6*6*6
            

Observations:

• The pattern consists of 7 rows.
• Numbers decrement from 6 to 3 in the upper half.
• The middle row (3) is repeated once.
• Each number is followed by a '*', except for the last number in each row.
• The lower half mirrors the upper half, incrementing from 4 to 6.

Algorithm

The pattern follows these steps:

1. Initialize a variable to determine the maximum number (N).
2. Loop through rows from N down to 3 to print the upper half of the diamond.
3. For each row, loop through columns (up to the current row number) and print the current row number.
4. Print the number followed by '*' except for the last number in the row.
5. After completing the upper half, print the middle row (3) again.
6. Loop through rows from 4 to N to print the lower half of the diamond.
7. Repeat steps 3 and 4 for the lower half.
8. Move to the next line after printing each row.

Method 1: Using Nested Loops

This method uses two loops to print the pattern.

public class DiamondNumberStarPatternSandwichInverted {
    public static void main(String[] args) {
        int n = 6;  // Maximum number for the diamond pattern

        // Loop to print the upper half of the diamond
        for (int i = n; i >= 3; i--) {  // Loop for each row
            for (int j = 1; j <= (n - i + 1); j++) {  // Loop for each column in the current row
                System.out.print(i);  // Print the current row number
                if (j < (n - i + 1)) System.out.print("*");  // Print '*' if not the last number in the row
            }
            System.out.println();  // Move to the next line after each row
        }

        // Print the middle row again
        System.out.println("3");  // Print the middle number

        // Loop to print the lower half of the diamond
        for (int i = 4; i <= n; i++) {  // Loop for each row
            for (int j = 1; j <= (i - 3); j++) {  // Loop for each column in the current row
                System.out.print(i);  // Print the current row number
                if (j < (i - 3)) System.out.print("*");  // Print '*' if not the last number in the row
            }
            System.out.println();  // Move to the next line after each row
        }
    }
}
            

Output:

6*6*6*6
5*5*5
4*4
3
3
4*4
5*5*5
6*6*6*6