Inverted Pyramid Star Pattern Logic

Turning the Pyramid Upside Down

Printing an inverted pyramid tests your ability to reverse both the space generation and the star generation logic simultaneously.

The Problem

Print an inverted pyramid of size N. If N = 3:

*****
 ***
  *

The Analysis (Mathematical Approach)

Let's map N = 3.

• Row 1: 0 spaces, 5 stars.
• Row 2: 1 space, 3 stars.
• Row 3: 2 spaces, 1 star.

The Space Formula: The spaces increase as the row increases. space = row - 1.

The Star Formula: The stars decrease by 2 each time. star = 2 * (N - row) + 1.

The Code Implementation (Formula Method)

int n = 3;
for (int row = 1; row <= n; row++) {
    for (int space = 1; space <= row - 1; space++) {
        System.out.print(" ");
    }
    for (int star = 1; star <= 2 * (n - row) + 1; star++) {
        System.out.print("*");
    }
    System.out.println();
}

The Simpler Approach (Reversing the Outer Loop)

Instead of recalculating complex formulas, you can literally take the exact code for a normal pyramid and just run the outer loop backward!

int n = 3;
// Start from N, go down to 1
for (int row = n; row >= 1; row--) {
    // The exact same inner loops as a normal pyramid!
    for (int space = 1; space <= n - row; space++) {
        System.out.print(" ");
    }
    for (int star = 1; star <= (2 * row) - 1; star++) {
        System.out.print("*");
    }
    System.out.println();
}

The Takeaway

In programming, if a problem is simply the reverse of a problem you already solved, don't rewrite the core logic. Just reverse the data flow (the outer loop). It is cleaner, faster, and infinitely less prone to math errors.