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Python Program to print a number diamond of any given size N in Rangoli Style
  • Difficulty Level : Medium
  • Last Updated : 31 Dec, 2020

Given an integer N, the task is to print a number diamond of size N in rangoli style where N means till Nth number from number ‘1’.

Examples:

Input : 
2
Output :
--2--
2-1-2
--2--

Input : 
3
Output :
----3----
--3-2-3--
3-2-1-2-3
--3-2-3--
----3----

Input :
4
Output :
------4------
----4-3-4----
--4-3-2-3-4--
4-3-2-1-2-3-4
--4-3-2-3-4--
----4-3-4----
------4------

Approach:
First of all print from the first row till middle row, and then print from the row after middle row till the last row. The total number of positions in each row will be 4(N-1) + 1. Number of rows will be 2(N-1) + 1. Time complexity is O(N^2).

Below is the implementation.




def print_diamond(size):
      
    # print the first triangle
    # (the upper half)
    for i in range (size):
          
        # print from first row till
        # middle row
        rownum = i + 1
        num_alphabet = 2 * rownum - 1
        space_in_between_alphabets = num_alphabet - 1
          
        total_spots = (2 * size - 1) * 2 - 1
        total_space = total_spots - num_alphabet
          
        space_leading_trailing = total_space - space_in_between_alphabets
        lead_space = int(space_leading_trailing / 2)
        trail_space = int(space_leading_trailing / 2)
          
        # print the leading spaces
        for j in range(lead_space):
            print('-', end ='')
          
        # determine the middle character
        mid_char = (1 + size - 1) - int(num_alphabet / 2)
          
        # start with the last character 
        k = 1 + size - 1
        is_alphabet_printed = False
        mid_char_reached = False
          
        # print the numbers alternated by '-'
        for j in range(num_alphabet + space_in_between_alphabets):
              
            if not is_alphabet_printed:
                print(str(k), end ='')
                is_alphabet_printed = True
                  
                if k == mid_char:
                    mid_char_reached = True
                  
                if mid_char_reached == True:
                    k += 1
                  
                else:
                    k -= 1
              
            else:
                print('-', end ='')
                is_alphabet_printed = False
          
        # print the trailing spaces
        for j in range(trail_space):
            print('-', end ='')
          
        # go to the next line
        print('')
      
    # print the rows after middle row 
    # till last row (the second triangle 
    # which is inverted, i.e., the lower half)
    for i in range(size + 1, 2 * size):
          
        rownum = i
        num_alphabet = 2 * (2 * size - rownum) - 1
        space_in_between_alphabets = num_alphabet - 1
          
        total_spots = (2 * size - 1) * 2 - 1
        total_space = total_spots - num_alphabet
          
        space_leading_trailing = total_space - space_in_between_alphabets
        lead_space = int(space_leading_trailing / 2)
        trail_space = int(space_leading_trailing / 2)
          
        # print the leading spaces
        for j in range(lead_space):
            print('-', end ='')
          
        mid_char = (1 + size - 1) - int(num_alphabet / 2)
          
        # start with the last char
        k = 1 + size - 1
        is_alphabet_printed = False
        mid_char_reached = False
          
        # print the numbers alternated by '-'
        for j in range(num_alphabet + space_in_between_alphabets):
              
            if not is_alphabet_printed:
                print(str(k), end ='')
                is_alphabet_printed = True
                  
                if k == mid_char:
                    mid_char_reached = True
                  
                if mid_char_reached == True:
                    k += 1
                  
                else:
                    k -= 1
              
            else:
                print('-', end ='')
                is_alphabet_printed = False
          
        # print the trailing spaces
        for j in range(trail_space):
            print('-', end ='')
          
        # go to the next line
        print('')
  
# Driver Code
if __name__ == '__main__':
      
    n = 5
    print_diamond(n)

Output:

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

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