Rotating Start Number Pattern in C++

Beginner
⏱️ 6 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
Nested Loops
Rotating start number pattern output (12345, 21234, 32123, 43212, 54321) in C++ programming

What You’ll Learn

How to print a pattern where each row starts with a descending prefix and then continues with ascending numbers:

12345, 21234, 32123, 43212, 54321.

This is a neat nested-loop exercise that combines descending and ascending sequences.

⭐ Pattern Output

For rows = 5, the pattern looks like this:

Output
12345
21234
32123
43212
54321
1

Complete C++ Program

First print i..2, then print 1..(rows+1-i).

C++
#include <iostream>
using namespace std;

int main() {
    int i, j, k;

    for (i = 1; i <= 5; i++) {
        for (j = i; j > 1; j--)
            cout << j;
        for (k = 1; k <= 6 - i; k++)
            cout << k;
        cout << "\n";
    }

    return 0;
}

🧠 How It Works

1

Outer loop chooses the row

i runs from 1 to 5, creating 5 rows.

Rows
2

Print the descending prefix

The first inner loop prints i, i-1, ... , 2. For i=4, it prints 432.

Prefix
3

Print the ascending suffix

The second inner loop prints 1..(rows+1-i). For i=4, it prints 12.

Suffix
4

Combine both parts

Together, the row becomes 432 + 12 = 43212.

Result
=

Rotating start

Each row keeps total length 5 while shifting the start digit forward.

2

Variation — User Input Version

Let the user choose the number of rows and print the same logic for any rows.

C++
#include <iostream>
using namespace std;

int main() {
    int rows;
    cout << "Enter the number of rows: ";
    cin >> rows;

    if (rows <= 0) return 0;

    for (int i = 1; i <= rows; i++) {
        for (int j = i; j > 1; j--)
            cout << j;

        for (int k = 1; k <= (rows + 1 - i); k++)
            cout << k;

        cout << "\n";
    }

    return 0;
}

💡 Tips for Enhancement

Try These

  • Add spaces between digits for readability
  • Print the pattern with leading spaces to make it a pyramid
  • Replace digits with letters for an alphabet version
  • Validate input (check cin.fail())
  • Create a mirror variant by changing the suffix direction

Avoid

  • Hard-coding 5 if you want a reusable program
  • Forgetting the newline after each row
  • Using endl in loops (extra flushing)
  • Mixing row/column logic (keep row in outer loop)

Key Takeaways

1

Row i prints a descending prefix from i to 2.

2

Then it prints an ascending suffix from 1 to rows+1-i.

3

Total row length stays constant (equal to rows).

4

Overall work is about O(n²) for n rows.

❓ Frequently Asked Questions

The prefix prints i-1 digits (from i down to 2) and the suffix prints rows-i+1 digits (from 1 to that value). Together they total rows.
Print a space after each digit and adjust the suffix/prefix accordingly (or build a string for each row).
Yes. Iterate i from rows down to 1 to reverse the row order.
O(n²) for n rows because each row prints \(n\) digits.

Explore More C++ Number Patterns!

Combining descending and ascending loops is a common trick for many “rotation” style patterns.

All Number Patterns →
Did you know?

You can think of each row as a small rotation: print backwards from i to 2, then wrap around and print from 1 upward.

About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
  • Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

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