Day 13 – Star Pattern Problems Solution

Q1 :- Reverse Right-Angled Triangle Made of Asterisks

Write a JavaScript function that prints the following reverse right-angled triangle pattern of asterisks, for a given positive integer n:

input

Input = n

Approach

1. Outer Loop

1. The outer loop is responsible for printing the rows.
2. It starts from n and continues as long as the value is greater than 0.
3. In each iteration, it runs the inner loop and then decreases the value of i by 1.

2. Inner Loop

1. The inner loop is responsible for printing the columns (like *, numbers, etc.).
2. It starts from 0 and continues until it is less than the current value of i (from the outer loop).
3. Since the outer loop decreases i in each step, the inner loop also runs fewer times in each new row.

Example (n = 4):

****
***
**
*

✅ Final JavaScript Solution

function printReverseTriangle(n) {
  let output = "";

  // Outer loop: from n down to 1
  for (let i = n; i > 0; i--) {
    // Inner loop: print i asterisks
    for (let j = 0; j < i; j++) {
      output += "*";
    }
    // Add a newline after each row
    output += "\n";
  }

  return output;
}

// Test it
console.log("Reverse Right-Angled Triangle Pattern for n = 4");
console.log(printReverseTriangle(4));

Q2: Reverse Right-Angled Triangle of Increasing Numbers

🧩 Problem Statement

Write a JavaScript program that prints a triangle made of numbers.

The triangle should be upside down (reverse right-angled) and the numbers in each row should start from 1 and go up.

🧠 Approach

To solve this pattern problem, we will use two loops — one for rows and one for numbers in each row.

---

✅ Outer Loop (Controls Rows)

1. The outer loop decides how many rows will be printed.
2. It starts from n and goes down to - 1, because we want the biggest row first.
3. Each time, it runs the inner loop to print the numbers.
4. After each row, we move to a new line.

---

✅ Inner Loop (Controls Numbers in a Row)

1. The inner loop prints numbers from 1 up to the current row number.
2. For example:
   • In the first row (i = 4), it prints 1 2 3 4
   • In the second row (i = 3), it prints 1 2 3
   • And so on...
3. We add a space after each number to keep them separated.

---

🧪 Example Flow (n = 4)

• Outer loop starts with i = 4
• Inner loop prints: 1 2 3 4
• Outer loop goes to i = 3
• Inner loop prints: 1 2 3
• ... continues until i = 1

---

Example

Input

Input = 4

Output

1 2 3 4
1 2 3
1 2
1

✅ Final JavaScript Solution

function Print_a_Reverse_Right_Angled_Triangle_With_Increasing_Number(n) {
  let Number = '';

  for (let i = n; i > 0; i--) {
    for (let j = 1; j <= i; j++) {
      Number += j + ' '; // Add a space after each number
    }
    Number += '\n'; // Move to the next row
  }

  return Number;
}

console.log(Print_a_Reverse_Right_Angled_Triangle_With_Increasing_Number(4));