Python Program to print hollow half diamond hash pattern

Difficulty Level : Easy
Last Updated : 31 Dec, 2020

Give an integer N and the task is to print hollow half diamond pattern.

Examples:

Input : 6
Output :
# 
# # 
#   # 
#     # 
#       # 
#         # 
#       # 
#     # 
#   # 
# # 
# 

Input : 7
Output :
# 
# # 
#   # 
#     # 
#       # 
#         # 
#           # 
#         # 
#       # 
#     # 
#   # 
# # 
#

Approach:
The idea is to break the pattern into two parts:

Upper part: For the upper half start the for loop with iterator (i) from 1 to n and one more for loop with iterator (j) from 1 to i.
```
# 
# # 
#   # 
#     # 
#       # 
#         # 
#           #  
```
Lower part: For lower half start the for loop with iterator (n-1) to 1 and loop inside this for will remain same as for the upper half.
```
#         # 
#       # 
#     # 
#   # 
# # 
#
```
Now we have to check this condition that if (i==j) or (j==1) then we have to print “#”, otherwise we have to print ” “(space).

Below is the implementation:

# python program to print  
# hollow half diamond star 
  
  
# function to print hollow 
# half diamond star 
def hollow_half_diamond(N): 
      
    # this for loop is for  
    # printing upper half  
    for i in range( 1, N + 1): 
        for j in range(1, i + 1): 
              
            # this is the condition to  
            # print "#" only on the 
            # boundaries 
            if i == j or j == 1: 
                print("#", end =" ") 
                  
            # print " "(space) on the rest 
            # of the area 
            else: 
                print(" ", end =" ") 
        print() 
      
    # this for loop is to print lower half 
    for i in range(N - 1, 0, -1): 
          
        for j in range(1, i + 1): 
              
            if j == 1 or i == j: 
                print("#", end =" ") 
              
            else: 
                print(" ", end =" ") 
          
        print() 
  
# Driver Code 
if __name__ == "__main__": 
    N = 7
    hollow_half_diamond( N ) 
  

Output:

# 
# # 
#   # 
#     # 
#       # 
#         # 
#           # 
#         # 
#       # 
#     # 
#   # 
# # 
#

Time Complexity: O(N^2)

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