Ruby Program to Print Numbers 1 to n

In Ruby, you can print numbers from 1 to n using a loop like for i in 1..n do puts i end where n is the limit.

Examples

Input3

Output1 2 3

Input1

Output1

Input0

Output

How to Think About It

To print numbers from 1 to n, start 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 loop from 1 to n

3

For each number in the loop, print the number

4

End the loop

Code

ruby

puts "Enter a number:"
n = gets.to_i
for i in 1..n do
  puts i
end

Output

Enter a number:
1
2
3

Dry Run

Let's trace input 3 through the code

1

Input n

User enters 3, so n = 3

2

Start loop

Loop from i = 1 to 3

3

Print i

Print 1

4

Next iteration

i = 2, print 2

5

Next iteration

i = 3, print 3

6

End loop

Loop ends after i = 3

i
1
2
3

Why This Works

Step 1: Getting input

We use gets.to_i to read the number n from the user and convert it to an integer.

Step 2: Looping through numbers

The for i in 1..n loop runs from 1 to n, including both ends.

Step 3: Printing each number

Inside the loop, puts i prints the current number on a new line.

Alternative Approaches

Using while loop

ruby

puts "Enter a number:"
n = gets.to_i
i = 1
while i <= n
  puts i
  i += 1
end

This uses a while loop instead of for; it is more flexible but slightly longer.

Using upto method

ruby

puts "Enter a number:"
n = gets.to_i
1.upto(n) { |i| puts i }

This is a Ruby-specific method that is concise and readable.

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

Time Complexity

The loop runs n times, printing each number once, so time grows linearly with n.

Space Complexity

Only a few variables are used, so space is constant regardless of n.

Which Approach is Fastest?

All approaches run in O(n) time; using upto is most idiomatic and concise in Ruby.

Approach	Time	Space	Best For
for loop	O(n)	O(1)	Simple and clear for beginners
while loop	O(n)	O(1)	More control over loop conditions
upto method	O(n)	O(1)	Concise and idiomatic Ruby code