Printing Patterns in Python

Pattern questions are very common in programming. These questions help in getting familiar with the flow of the programs and also help in understanding how to write programs to get the desired output. Patterns are printed using loops. We generally use nested loops to print a pattern. The outer loop defines the number of rows of the pattern. At the same time, the inner loop defines the pattern we need. We put conditions in the inner loop. In this tutorial, we will see programs to print different kinds of patterns. There can be more than one way to print a pattern, so there is no need to follow one strict approach.

Simple Pyramid Pattern

Approach - 1

Code

Output:

 * * * * * * * * * * * * * * * 

Time Complexity: The time complexity of this approach is non-linear. We have used nested loops to print the pattern. The outer loop will iterate n times; hence, the time complexity will be O(n). However, the inner loop will iterate from 0 to n times, which makes the worst time complexity of the inner loop O(n). The total time complexity of this program is O(n2).

Space Complexity: The space complexity of this approach is O(1). We have not used any auxiliary space to print the pattern.

Approach - 2

We can print the same pattern using a list, which simplifies the code.

Code

Output:

 * * * * * * * * * * * * * * * 

Time Complexity: The time complexity of this approach is linear because we have used a single loop to print the pattern. Therefore, using a list is better than using nested loops. The join function has a time complexity of O(n); however, when taken in total, the complexity will be O(n) + O(n). The average time complexity of this approach is O(n).

Space Complexity: The space complexity of this approach is linear because we have used a list to store the pattern. Therefore, the space complexity of this approach is O(n)

Approach - 3

We will use the recursion method to print the pattern.

Code

Output:

 * * * * * * * * * * * * * * * 

Approach - 4

This time, we will use the while loop to print the pattern.

Code

Output:

 * * * * * * * * * * * * * * * 

Time Complexity: The time complexity of this approach is O(n ^ 2). We have used nested loops to print the pattern.

Space Complexity: The space complexity of this approach is O(1) since we have not used any extra space to store the pattern.

Rotating the Pattern

Now, we will flip the pattern and design the programs to print the pattern.

Approach - 1

Code

Output:

 * * * * * * * * * * * * * * * 

Approach - 2

Now, we will see a better approach to printing the previous pattern

In this pattern, we must print spaces (number_from_base - row_number) and then the stars row_number times. This time, we will use the while loop to print the pattern. We will see that we can print the pattern using a single while loop and hence don't require nested loops. This will decrease the time complexity from non-linear to linear time complexity. Below is the Python code for the implementation of this approach

Code

Output:

 * * * * * * * * * * * * * * * 

Approach - 3

We will write the previous program using the for loop.

Code

Output:

 * * * * * * * * * * * * * * * 

Printing Triangle

Approach - 1

Code

Output:

 * * * * * * * * * * * * * * * 

Number Pattern

Now, we will see how to print the pattern using numbers.

Approach - 1

Code

Output:

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

Approach - 2

In this pattern, we do not have to start the pattern with 1 in each row.

Code

Output:

 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 

Approach - 3

In this pattern, we will print a triangle using the numbers.

Code

Output:

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

Printing Alphabets

Pattern - 1

We will print patterns using alphabets. We will update the ASCII code of the letters to print alphabet patterns. The reason to use ASCII code is to increment the characters.

Code

Output:

 A B B C C C D D D D E E E E E 

Pattern - 2

Instead of starting with an A in each row, this program will print the alphabet continuously. Compared with the previous algorithm, the change will be in the increment of the character ASCII code. In the previous code, we incremented the code value after the completion t=of the inner loop, i.e., in the outer loop. This algorithm will increment the code value for every row. In this algorithm, we will increment the code value in the inner loop, hence moving to the next character for each column of each row.

Code

Output:

 A B C D E F G H I J K L M N O 

Pattern - 3

In this pattern, we will print a triangle of characters.

Code

Output:

 A A B A B C A B C D A B C D E 

Complex Patterns

Pattern - 1

This program is divided into four parts.

Code

Output:

Pattern - 2

Code

Output:

Pattern - 3

Code

Output:

Pattern - 4

Code

Output:

 \*******/ *\*****/* **\***/** ***\*/*** ****/**** ***/*\*** **/***\** */*****\* /*******\ 

Pattern - 5

Code

Output:

 4 3 2 1 0 3 2 1 0 2 1 0 1 0 0 

Pattern - 6

Code

Output:

 1 7 2 12 8 3 16 13 9 4 19 17 14 10 5 21 20 18 15 11 6 

Print G Pattern

We shall discover the procedures if we attempt to analyze this image using a (row, column) matrix, where the circles denote the locations of the stars in the pattern G. In this case, the procedures are carried out column-by-column. Therefore, we set the first if condition for the first line of stars, which states that all rows from 1 to (n-1) will receive the stars and that rows with 0 and (n-1) will not. Similarly, we want stars in the second, third, and fourth columns at row = 0 and row = (n-1). The remaining steps are self-explanatory and are clear from the diagram's row and column placement.

Below is the implementation of this approach in Python.

Code

Output: