🚀 Programming Example

Logic to print the given number pattern 12345 1234 123 12 1

4,642 Views

Beginner

Code Snippet

Write a C program to print the given number pattern using loop. How to print the given triangular number pattern using for loop in C programming. Logic to print the given number pattern using loop in C program.

💻 Program Code

/**
 * C program to print number pattern
 * www.rummanansari.com 
 */

#include <stdio.h>

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

    printf("Enter N: ");
    scanf("%d", &N);

    for(i=1; i<=N; i++)
    {
        // Logic to print numbers
        for(j=1; j<=N-i+1; j++)
        {
            printf("%d", j);
        }

        printf("\n");
    }

    return 0;
}

🖥 Program Output

📘 Explanation

C PROGRAMMING

Print a Reverse Decreasing Number Pattern in C

Learn how to use nested loops in C programming to generate a decreasing number pattern such as 12345, 1234, 123, 12, and 1.

Objective

In this program, the user enters a number N. The program prints numbers from 1 to N on the first line and decreases one number on each subsequent line. This example helps beginners understand nested loops and pattern generation techniques.

Pattern programs are one of the best ways to master loops and iteration logic in C programming.

Prerequisites

Before Learning This Program

Basic understanding of C programming syntax
Knowledge of variables and data types
Understanding of for loops
Basic input and output using scanf() and printf()
Understanding of nested loops

Program Code


#include 

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

    printf("Enter N: ");
    scanf("%d", &N);

    for(i=1; i<=N; i++)
    {
        for(j=1; j<=N-i+1; j++)
        {
            printf("%d", j);
        }

        printf("\n");
    }

    return 0;
}

Sample Input


Enter N: 5

Output

How the Program Works

User Inputs N

The user enters the number of rows to print.

The value entered by the user is stored in the variable N.

Outer Loop Controls Rows

One iteration represents one row.

The outer loop runs from 1 to N and determines how many rows are displayed.

Inner Loop Prints Numbers

Creates the actual pattern.

The inner loop prints numbers from 1 to (N − i + 1). Therefore each row contains one less number than the previous row.

Move to Next Line

End of row processing.

The statement printf("\n"); moves the cursor to the next line after a row is completed.

Pattern Formula

ROWS

Total Numbers in Row = N - i + 1

Here:

N = Total rows entered by the user
i = Current row number

Loop Execution Table

Row (i)	N - i + 1	Numbers Printed
1	5	12345
2	4	1234
3	3	123
4	2	12
5	1	1

Visual Representation


Row 1 -> 12345
Row 2 -> 1234
Row 3 -> 123
Row 4 -> 12
Row 5 -> 1

Simple Analogy

Imagine a staircase where each step becomes shorter than the previous one. Similarly, each new row prints one less number.

Complexity Analysis

Metric	Complexity
Time Complexity	O(N²)
Space Complexity	O(1)

Key Learning Outcomes

After Completing This Program You Will Understand

How nested loops work
How rows and columns are controlled in pattern programming
How mathematical expressions can be used inside loop conditions
How to generate decreasing number patterns
How to build logic for advanced pattern problems

Key Takeaway

Pattern programs help developers build strong loop logic. This program demonstrates how an inner loop can dynamically reduce the number of values printed in each row using the formula N - i + 1.

🎯 How to learn from this example

First understand the algorithm carefully. Then study the program line-by-line and compare it with the output. Finally, review the explanation section to strengthen your logic and programming understanding.

🔥 Practice suggestion

Rewrite the program without looking at the code. Modify values, conditions or logic and run it again. This helps improve confidence and strengthens coding skills much faster.