Learning

Pattern Printing Problems

Core Concept: Nested Loops

Patterns are built with two loops:

Outer loop → controls ROWS
Inner loop → controls COLUMNS (what prints on each row)

python

# Basic square pattern
n = 5
for i in range(n):          # Rows
    for j in range(n):      # Columns
        print('*', end=' ')
    print()  # New line after each row

# * * * * *
# * * * * *
# * * * * *
# * * * * *
# * * * * *

Right-Angled Triangle

python

n = 5
for i in range(1, n + 1):
    for j in range(i):
        print('*', end=' ')
    print()

# *
# * *
# * * *
# * * * *
# * * * * *

# Using string multiplication (simpler!)
for i in range(1, n + 1):
    print('* ' * i)

Inverted Triangle

python

n = 5
for i in range(n, 0, -1):
    print('* ' * i)

# * * * * *
# * * * *
# * * *
# * *
# *

Pyramid (Full Triangle)

python

n = 5
for i in range(1, n + 1):
    spaces = '  ' * (n - i)
    stars = '* ' * i
    print(spaces + stars)

#         *
#       * *
#     * * *
#   * * * *
# * * * * *

Diamond Pattern

python

n = 5
# Upper half
for i in range(1, n + 1):
    print('  ' * (n - i) + '* ' * i)

# Lower half
for i in range(n - 1, 0, -1):
    print('  ' * (n - i) + '* ' * i)

Number Patterns

python

# Floyd's Triangle
n = 5
num = 1
for i in range(1, n + 1):
    for j in range(i):
        print(f'{num:3}', end='')
        num += 1
    print()

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

# Number triangle
n = 5
for i in range(1, n + 1):
    for j in range(1, i + 1):
        print(j, end=' ')
    print()

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

# Binary triangle
for i in range(1, n + 1):
    for j in range(i):
        print(j % 2, end=' ')
    print()

# 0
# 0 1
# 0 1 0
# 0 1 0 1
# 0 1 0 1 0

Character Patterns

python

# Alphabet triangle
n = 5
for i in range(1, n + 1):
    ch = 65  # ASCII for 'A'
    for j in range(i):
        print(chr(ch), end=' ')
        ch += 1
    print()

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

# Repeated character triangle
for i in range(1, n + 1):
    print((chr(64 + i) + ' ') * i)

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

Hollow Patterns

python

# Hollow square
n = 5
for i in range(n):
    for j in range(n):
        if i == 0 or i == n-1 or j == 0 or j == n-1:
            print('*', end=' ')
        else:
            print(' ', end=' ')
    print()

# * * * * *
# *       *
# *       *
# *       *
# * * * * *

Key Formula Summary

| Pattern | Spaces | Stars | Formula | |---------|--------|-------|---------| | Right triangle | 0 | i | * * i | | Inverted | 0 | n-i+1 | * * (n-i+1) | | Pyramid | n-i | i | ' '*(n-i) + '* '*i | | Diamond | abs(n-i) | n-abs(n-i) | Varies |

Key Rules

•Outer loop = rows, inner loop = columns — always think in this 2D grid
•String multiplication ('* ' * i) is cleaner than nested loops for simple patterns
•For pyramid: spaces decrease (n-i) while stars increase (i) — they must sum to n
•Hollow patterns: print star ONLY on first/last row OR first/last column
•Use chr(65) for 'A', chr(97) for 'a' — increment for next character
•Use f'{num:width}' or end=' ' to maintain alignment in number patterns

Your Task

Create a function `print_pattern(n, type)` that prints different patterns based on type: 'triangle' (right-angled), 'pyramid', 'diamond', 'hollow_square'. Each function should use nested loops (not just string multiplication). Also create `number_triangle(n)` that prints Floyd's triangle with proper spacing alignment.

Learning

Pattern Printing Problems

Core Concept: Nested Loops

Patterns are built with two loops:

Outer loop → controls ROWS
Inner loop → controls COLUMNS (what prints on each row)

python

# Basic square pattern
n = 5
for i in range(n):          # Rows
    for j in range(n):      # Columns
        print('*', end=' ')
    print()  # New line after each row

# * * * * *
# * * * * *
# * * * * *
# * * * * *
# * * * * *

Right-Angled Triangle

python

n = 5
for i in range(1, n + 1):
    for j in range(i):
        print('*', end=' ')
    print()

# *
# * *
# * * *
# * * * *
# * * * * *

# Using string multiplication (simpler!)
for i in range(1, n + 1):
    print('* ' * i)

Inverted Triangle

python

n = 5
for i in range(n, 0, -1):
    print('* ' * i)

# * * * * *
# * * * *
# * * *
# * *
# *

Pyramid (Full Triangle)

python

n = 5
for i in range(1, n + 1):
    spaces = '  ' * (n - i)
    stars = '* ' * i
    print(spaces + stars)

#         *
#       * *
#     * * *
#   * * * *
# * * * * *

Diamond Pattern

python

n = 5
# Upper half
for i in range(1, n + 1):
    print('  ' * (n - i) + '* ' * i)

# Lower half
for i in range(n - 1, 0, -1):
    print('  ' * (n - i) + '* ' * i)

Number Patterns

python

# Floyd's Triangle
n = 5
num = 1
for i in range(1, n + 1):
    for j in range(i):
        print(f'{num:3}', end='')
        num += 1
    print()

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

# Number triangle
n = 5
for i in range(1, n + 1):
    for j in range(1, i + 1):
        print(j, end=' ')
    print()

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

# Binary triangle
for i in range(1, n + 1):
    for j in range(i):
        print(j % 2, end=' ')
    print()

# 0
# 0 1
# 0 1 0
# 0 1 0 1
# 0 1 0 1 0

Character Patterns

python

# Alphabet triangle
n = 5
for i in range(1, n + 1):
    ch = 65  # ASCII for 'A'
    for j in range(i):
        print(chr(ch), end=' ')
        ch += 1
    print()

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

# Repeated character triangle
for i in range(1, n + 1):
    print((chr(64 + i) + ' ') * i)

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

Hollow Patterns

python

# Hollow square
n = 5
for i in range(n):
    for j in range(n):
        if i == 0 or i == n-1 or j == 0 or j == n-1:
            print('*', end=' ')
        else:
            print(' ', end=' ')
    print()

# * * * * *
# *       *
# *       *
# *       *
# * * * * *

Key Formula Summary

Key Rules

•Outer loop = rows, inner loop = columns — always think in this 2D grid
•String multiplication ('* ' * i) is cleaner than nested loops for simple patterns
•For pyramid: spaces decrease (n-i) while stars increase (i) — they must sum to n
•Hollow patterns: print star ONLY on first/last row OR first/last column
•Use chr(65) for 'A', chr(97) for 'a' — increment for next character
•Use f'{num:width}' or end=' ' to maintain alignment in number patterns

Your Task