#include <iostream>
using namespace std;

int main() {
    int rows;
    
    cout << "Enter number of rows: ";
    cin >> rows;
    
    for (int i = 1; i <= rows; i++) {
        for (int j = 1; j <= i; j++) {
            cout << j << " ";
        }
        cout << endl;
    }
    
    return 0;
}

Enter number of rows: 5
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5

Number Pattern in C++

This program teaches you how to print a number pattern using nested loops in C++. Instead of printing stars, this pattern prints numbers in a sequential order. Each row displays numbers from 1 up to the row number, creating a triangular number pattern. This is an excellent way to understand how to use loop variables in output and transition from character patterns to number patterns.

What is a Number Pattern?

A number pattern looks like this (for 5 rows):

1
1 2
1 2 3
1 2 3 4
1 2 3 4 5

Notice:

• Each row starts from 1
• Each row ends at the row number
• Row 1 has numbers 1
• Row 2 has numbers 1, 2
• Row 3 has numbers 1, 2, 3
• And so on...

Understanding the Pattern Logic

The key insight is: ## In row i, we print numbers from 1 to i.

This means:

• Row 1: Print 1 to 1 → 1
• Row 2: Print 1 to 2 → 1 2
• Row 3: Print 1 to 3 → 1 2 3
• Row 4: Print 1 to 4 → 1 2 3 4
• Row 5: Print 1 to 5 → 1 2 3 4 5

Key Difference: Printing j vs Printing i

This is an important concept:

• cout << j; → Prints the inner loop variable (1, 2, 3, 4, 5...)

• cout << i; → Would print the outer loop variable (1, 2, 2, 2, 3, 3, 3, 3...)

Using j gives us the sequential number pattern we want.

Summary

• The outer loop (i) controls which row we're printing (1 to rows).
• The inner loop (j) runs from 1 to i, printing each number.
• We print j (not i) to get sequential numbers 1, 2, 3, 4...
• After each row, endl moves to the next line.
• This creates a number pattern where each row contains numbers from 1 to the row number.

This program is essential for understanding how to use loop variables in output and creating numeric patterns. It's a foundation for more complex number patterns and mathematical visualizations.