How to Print an Inverted Right-Angled Triangle Pattern

Inverting the Logic

Once you can print a standard triangle, printing an inverted one is a simple exercise in reversing mathematical logic.

The Problem

Print an inverted triangle of size N. If N = 4:

****
***
**
*

The Analysis

1. Rows: There are exactly N rows. Outer loop runs from 1 to N.
2. Columns: Look at the relationship.
   • Row 1 has 4 stars.
   • Row 2 has 3 stars.
   • Row 3 has 2 stars.
3. Relationship: As the row increases, the stars decrease. The mathematical formula connecting them is N - row + 1.
   • If N=4, Row 1 = 4 - 1 + 1 = 4.
   • If N=4, Row 2 = 4 - 2 + 1 = 3.

The Code Implementation (Method 1: Formula)

int n = 4;
for (int row = 1; row <= n; row++) {
    // Using the derived mathematical formula
    for (int col = 1; col <= n - row + 1; col++) {
        System.out.print("*");
    }
    System.out.println();
}

The Code Implementation (Method 2: Reverse Outer Loop)

Instead of complex math, you can just reverse the outer loop!

int n = 4;
// Start at N, go down to 1
for (int row = n; row >= 1; row--) {
    // Inner loop logic stays exactly the same as a normal triangle
    for (int col = 1; col <= row; col++) {
        System.out.print("*");
    }
    System.out.println();
}

The Takeaway

There are multiple ways to solve a pattern. You can either construct a complex mathematical boundary for your inner loop, or you can invert the direction of your outer loop to keep the inner logic simple. Flexibility is key.