Program to print the Fish Pattern

Given an integer N, the task is to print a pattern of fish over 2N+1 rows.

Example:

Input: N=3
Output:
        *      
      ***    *
   *****  **
**********
   *****  **
      ***    *
        *      

Input: N=5
Output:
              *          
            ***        *
         *****      **
      *******    ***
   *********  ****
****************
   *********  ****
      *******    ***
         *****      **
            ***        *
              *     

Approach: The fish consists of three parts:

• Upper Part: Over N rows.
• Middle Part: Singe row in the middle
• Lower Part: Over N rows

Now, let’s try to understand the pattern using an example:
For N=3, the fish is:

Now, to solve this question, follow the steps below:

1. First, create the upper part:
   • Run a loop for i=0 to i<N, and in each iteration of the loop:
     • As depicted in the above image that first a string, say spaces1 having M (initially M=N) spaces appear, then a layer of stars, let’s say stars1 having only 1 star, then the string spaces1 appears 2 times (having 2*M spaces) and then another layer of stars, say stars2 having 0 stars initially.
     • Now in each iteration, spaces1 got reduced by a space, stars1 got increased by 2 stars and stars2 by 1 star.
2. For the middle part, just print both stars1 and stars2, as no spaces appear in this row.
3. Now, to get the lower part, reverse the algorithm for the upper part.
4. After the loop ends, the pattern of fish will be created.

Below is the implementation of the above approach.

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

Time Complexity: O(N)
Auxiliary Space: O(N)