Python Program to Print Number Triangle Pattern

You can print a number triangle pattern in Python using nested loops like for i in range(1, n+1): print(' '.join(str(x) for x in range(1, i+1))) where n is the number of rows.

Examples

Input3

Output1 1 2 1 2 3

Input5

Output1 1 2 1 2 3 1 2 3 4 1 2 3 4 5

Input1

Output1

How to Think About It

To print a number triangle pattern, think of printing rows from 1 to n. For each row, print numbers starting from 1 up to the current row number. Use one loop to go through each row and another loop inside it to print the numbers for that row.

Algorithm

1

Get the number of rows (n) as input.

2

For each row from 1 to n:

3

Print numbers starting from 1 up to the current row number separated by spaces.

4

Move to the next line after printing each row.

Code

python

n = int(input('Enter number of rows: '))
for i in range(1, n + 1):
    for j in range(1, i + 1):
        print(j, end=' ')
    print()

Output

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

Dry Run

Let's trace the program for input n=3 to see how it prints the number triangle.

1

Input

User inputs n = 3

2

First row (i=1)

Print numbers from 1 to 1: prints '1 '

3

Second row (i=2)

Print numbers from 1 to 2: prints '1 2 '

4

Third row (i=3)

Print numbers from 1 to 3: prints '1 2 3 '

Row (i)	Numbers Printed
1	1
2	1 2
3	1 2 3

Why This Works

Step 1: Outer loop controls rows

The outer for loop runs from 1 to n, controlling how many rows to print.

Step 2: Inner loop prints numbers

The inner for loop prints numbers from 1 up to the current row number i.

Step 3: Print moves to next line

After printing each row, print() moves the cursor to the next line for the next row.

Alternative Approaches

Using list comprehension and join

python

n = int(input('Enter number of rows: '))
for i in range(1, n + 1):
    print(' '.join(str(x) for x in range(1, i + 1)))

This method is concise and uses string joining to print each row in one line.

Using while loops

python

n = int(input('Enter number of rows: '))
i = 1
while i <= n:
    j = 1
    while j <= i:
        print(j, end=' ')
        j += 1
    print()
    i += 1

This uses while loops instead of for loops, which some beginners find easier to understand.

Complexity: O(n^2) time, O(1) space

Time Complexity

The program uses nested loops: the outer loop runs n times and the inner loop runs up to n times in the last iteration, resulting in O(n^2) time.

Space Complexity

The program uses constant extra space, only variables for counters, so space complexity is O(1).

Which Approach is Fastest?

Both for-loop and while-loop approaches have the same time and space complexity; the list comprehension method is more concise but similar in performance.

Approach	Time	Space	Best For
Nested for loops	O(n^2)	O(1)	Clear and easy to understand
List comprehension with join	O(n^2)	O(1)	Concise and readable
Nested while loops	O(n^2)	O(1)	Beginners learning loop basics