Mirror Number Pyramid in C++

Beginner
⏱️ 6 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
Nested Loops
Mirror number pyramid output (1, 212, 32123, 4321234, 543212345) in C++ programming

What You’ll Learn

How to print a mirror number pyramid in C++ such as 32123 and 543212345.

Each row is built in two parts: a descending sequence from i down to 2, followed by an ascending sequence from 1 up to i.

⭐ Pattern Output

For rows = 5, the pattern looks like this:

Output
1
212
32123
4321234
543212345
1

Complete C++ Program

Two inner loops: one prints the left (descending) half, the other prints the right (ascending) half.

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

int main() {
    int rows = 5;
    int i, j;

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

    return 0;
}

🧠 How It Works

1

Choose the row count

rows = 5 sets how many lines will be printed.

Setup
2

Outer loop controls the row

for (i = 1; i <= rows; i++) moves from row 1 to row rows.

Row control
3

Print the descending half

for (j = i; j > 1; j--) prints i, i-1, ..., 2.

Left side
4

Print the ascending half

for (j = 1; j <= i; j++) prints 1, 2, ..., i right after the descending half.

Right side
=

Mirror number pyramid

Row i prints 2i-1 digits, so total work across all rows is O(n²).

2

Variation — User Input Version

Let the user choose the number of rows using cin:

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

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

    cout << "Enter the number of rows: ";
    cin >> rows;

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

    return 0;
}

💡 Tips for Enhancement

Try These

  • Add spaces between numbers for readability (e.g., print j << ' ')
  • Right-align the pyramid by printing leading spaces before each row
  • Start from a different peak value (use a base offset in the printed numbers)
  • Print characters instead of numbers to make an alphabet mirror pattern
  • Build each row into a string for easier formatting

Avoid

  • Printing the center 1 twice (ensure the left loop stops at 2)
  • Using negative or zero rows without validation
  • Forgetting the newline after each row
  • Overcomplicating the logic—two simple loops are enough

Key Takeaways

1

Each row is made from a descending part and an ascending part.

2

The descending loop prints i..2, so the center 1 appears only once.

3

Row i prints 2i-1 digits (odd length), creating the mirror effect.

4

Total time grows quadratically with rows: O(n²).

❓ Frequently Asked Questions

It stops at j > 1 so that the center 1 is printed only once by the second loop.
Yes. Print a space after each number in both loops. If you want perfect formatting without a trailing space, build the row into a string.
Print leading spaces based on rows - i before the two loops. That shifts the pyramid toward the center.
O(n²) for n rows: each row prints 2i-1 characters.

Explore More C++ Number Patterns!

Try combining mirror logic with spacing and alignment to build more pyramid-style patterns.

All Number Patterns →
Did you know?

Many “palindrome” patterns are just two loops back-to-back: one loop for the left side and another for the right side. Keeping them separate makes the logic easier to reason about.

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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