C# Program to Print Numbers 1 to n

Use a for loop in C# like for (int i = 1; i <= n; i++) Console.WriteLine(i); to print numbers from 1 to n.

Examples

Input1

Output1

Input5

Output1 2 3 4 5

Input0

Output

How to Think About It

To print numbers from 1 to n, start counting from 1 and keep increasing by 1 until you reach n. For each number, print it on a new line. If n is zero or less, print nothing.

Algorithm

1

Get the input number n.

2

Start a counter i at 1.

3

While i is less than or equal to n, do:

4

Print the value of i.

5

Increase i by 1.

6

Stop when i becomes greater than n.

Code

csharp

using System;

class Program
{
    static void Main()
    {
        int n = 5; // Change this value to print up to n
        for (int i = 1; i <= n; i++)
        {
            Console.WriteLine(i);
        }
    }
}

Output

1
2
3
4
5

Dry Run

Let's trace printing numbers from 1 to 5 through the code

1

Initialize n and i

n = 5, i = 1

2

Check condition i <= n

1 <= 5 is true, so print 1

3

Increment i

i becomes 2

4

Repeat check and print

2 <= 5 true, print 2; i=3 3 <= 5 true, print 3; i=4 4 <= 5 true, print 4; i=5 5 <= 5 true, print 5; i=6

5

Stop loop

6 <= 5 false, loop ends

i	Condition i <= n	Action
1	true	Print 1
2	true	Print 2
3	true	Print 3
4	true	Print 4
5	true	Print 5
6	false	Stop

Why This Works

Step 1: Start from 1

We begin counting at 1 because the task is to print numbers starting from 1.

Step 2: Use a loop to repeat

The for loop repeats printing and increasing the number until it reaches n.

Step 3: Stop after n

The loop stops when the number goes beyond n, ensuring only numbers from 1 to n are printed.

Alternative Approaches

while loop

csharp

using System;

class Program
{
    static void Main()
    {
        int n = 5;
        int i = 1;
        while (i <= n)
        {
            Console.WriteLine(i);
            i++;
        }
    }
}

This uses a <code>while</code> loop instead of <code>for</code>, which is equally clear but separates initialization and increment.

recursion

csharp

using System;

class Program
{
    static void PrintNumbers(int i, int n)
    {
        if (i > n) return;
        Console.WriteLine(i);
        PrintNumbers(i + 1, n);
    }

    static void Main()
    {
        int n = 5;
        PrintNumbers(1, n);
    }
}

This uses recursion to print numbers, which is elegant but less efficient for large n due to call stack use.

Complexity: O(n) time, O(1) space

Time Complexity

The loop runs from 1 to n, so it executes n times, making the time complexity O(n).

Space Complexity

Only a few variables are used regardless of n, so space complexity is O(1).

Which Approach is Fastest?

The for loop and while loop have similar performance; recursion is less efficient due to function call overhead.

Approach	Time	Space	Best For
for loop	O(n)	O(1)	Simple and clear counting
while loop	O(n)	O(1)	When loop condition is complex or variable
recursion	O(n)	O(n)	Elegant but not for large n due to stack use