Python program to show diamond pattern with 2n-1 lines

A diamond pattern is a symmetric arrangement of asterisks that expands from one star to n stars, then contracts back to one star. The pattern consists of 2n-1 lines total, with the widest part containing n asterisks.

Understanding the Pattern

For n = 5, the diamond pattern looks like ?

    *
   * *
  * * *
 * * * *
* * * * *
 * * * *
  * * *
   * *
    *

The pattern has two parts ?

• Expanding part: Lines 1 to n (1, 2, 3, ..., n asterisks)
• Contracting part: Lines n+1 to 2n-1 (n-1, n-2, ..., 1 asterisks)

Algorithm

To create the diamond pattern ?

• For i from 1 to n: print i asterisks centered in 2n-1 character width
• For i from n-1 to 1: print i asterisks centered in 2n-1 character width

Implementation

def solve(n):
    # Expanding part (1 to n asterisks)
    for i in range(1, n + 1):
        print(('* ' * i).center(2 * n - 1))
    
    # Contracting part (n-1 to 1 asterisks)
    for i in range(n - 1, 0, -1):
        print(('* ' * i).center(2 * n - 1))

# Test with n = 5
n = 5
solve(n)

    *
   * *
  * * *
 * * * *
* * * * *
 * * * *
  * * *
   * *
    *

How It Works

The center() method centers the string within the specified width. For each line ?

• '* ' * i creates a string with i asterisks separated by spaces
• .center(2 * n - 1) centers this string in a field of width 2n-1
• The width 2n-1 ensures proper spacing for the diamond shape

Example with Different Values

def solve(n):
    for i in range(1, n + 1):
        print(('* ' * i).center(2 * n - 1))
    for i in range(n - 1, 0, -1):
        print(('* ' * i).center(2 * n - 1))

# Test with n = 3
print("Diamond pattern for n = 3:")
solve(3)

print("\nDiamond pattern for n = 7:")
solve(7)

Diamond pattern for n = 3:
  *
 * *
* * *
 * *
  *

Diamond pattern for n = 7:
      *
     * *
    * * *
   * * * *
  * * * * *
 * * * * * *
* * * * * * *
 * * * * * *
  * * * * *
   * * * *
    * * *
     * *
      *

Conclusion

The diamond pattern uses Python's center() method to create symmetric spacing. The pattern always has 2n-1 lines with the middle line containing n asterisks, creating a perfect diamond shape.