Adding hash algorithms
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Carlos Gutierrez
207
examples/hash_tables_demo.py
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207
examples/hash_tables_demo.py
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"""
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Demonstration of hash table implementations and their usage.
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"""
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import sys
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import os
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sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..'))
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from src.hash_tables import (
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DirectAddressTable,
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HashTableOpenAddressing,
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HashTableSeparateChaining
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)
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from src.hash_functions import (
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division_hash,
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string_hash_polynomial,
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string_hash_simple
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)
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def demo_direct_address_table():
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"""Demonstrate direct-address table."""
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print("=" * 60)
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print("Direct-Address Table Demonstration")
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print("=" * 60)
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# Create table for keys in range [0, 99]
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table = DirectAddressTable(100)
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# Insert some values
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table.insert(5, "Alice")
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table.insert(42, "Bob")
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table.insert(99, "Charlie")
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print("\nInserted key-value pairs:")
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print(" Key 5 ->", table.search(5))
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print(" Key 42 ->", table.search(42))
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print(" Key 99 ->", table.search(99))
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# Search
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print("\nSearching for key 42:", table.search(42))
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print("Searching for key 10:", table.search(10)) # Not found
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# Delete
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table.delete(42)
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print("\nAfter deleting key 42:")
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print(" Key 42 ->", table.search(42)) # None
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print()
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def demo_open_addressing():
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"""Demonstrate open addressing hash table."""
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print("=" * 60)
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print("Open Addressing Hash Table Demonstration")
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print("=" * 60)
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# Test with linear probing
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print("\n--- Linear Probing ---")
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ht_linear = HashTableOpenAddressing(10, probe_type='linear')
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keys = [10, 22, 31, 4, 15, 28, 17, 88, 59]
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for key in keys:
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ht_linear.insert(key, f"Value_{key}")
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print(f"Inserted {len(keys)} keys")
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print(f"Load factor: {ht_linear._load_factor():.2f}")
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print("\nSearching for keys:")
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for key in [10, 22, 88, 99]:
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result = ht_linear.search(key)
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print(f" Key {key}: {'Found' if result else 'Not found'}")
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# Test with quadratic probing
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print("\n--- Quadratic Probing ---")
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# Use larger table size for quadratic probing to avoid probe sequence issues
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ht_quad = HashTableOpenAddressing(20, probe_type='quadratic')
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for key in keys:
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ht_quad.insert(key, f"Value_{key}")
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print(f"Inserted {len(keys)} keys")
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print(f"Load factor: {ht_quad._load_factor():.2f}")
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# Test with double hashing
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print("\n--- Double Hashing ---")
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# Use larger table size for double hashing to ensure all keys can be inserted
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ht_double = HashTableOpenAddressing(20, probe_type='double')
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for key in keys:
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ht_double.insert(key, f"Value_{key}")
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print(f"Inserted {len(keys)} keys")
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print(f"Load factor: {ht_double._load_factor():.2f}")
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print()
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def demo_separate_chaining():
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"""Demonstrate separate chaining hash table."""
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print("=" * 60)
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print("Separate Chaining Hash Table Demonstration")
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print("=" * 60)
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ht = HashTableSeparateChaining(10)
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keys = [10, 22, 31, 4, 15, 28, 17, 88, 59, 71]
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for key in keys:
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ht.insert(key, f"Value_{key}")
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print(f"\nInserted {len(keys)} keys")
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print(f"Load factor: {ht._load_factor():.2f}")
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chain_lengths = ht.get_chain_lengths()
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print(f"Chain lengths: {chain_lengths}")
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print(f"Average chain length: {sum(chain_lengths) / len(chain_lengths):.2f}")
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print(f"Maximum chain length: {max(chain_lengths)}")
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print("\nSearching for keys:")
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for key in [10, 22, 88, 99]:
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result = ht.search(key)
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print(f" Key {key}: {'Found' if result else 'Not found'}")
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# Delete some keys
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print("\nDeleting keys 22 and 88:")
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ht.delete(22)
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ht.delete(88)
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print(f" Key 22: {'Found' if ht.search(22) else 'Not found'}")
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print(f" Key 88: {'Found' if ht.search(88) else 'Not found'}")
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print()
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def demo_hash_functions():
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"""Demonstrate different hash functions."""
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print("=" * 60)
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print("Hash Function Demonstration")
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print("=" * 60)
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keys = [10, 22, 31, 4, 15, 28, 17, 88, 59, 71]
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table_size = 11
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print(f"\nKeys: {keys}")
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print(f"Table size: {table_size}\n")
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# Division method
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print("Division method (h(k) = k mod m):")
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for key in keys[:5]:
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hash_val = division_hash(key, table_size)
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print(f" h({key}) = {hash_val}")
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# String hashing
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print("\nString hash functions:")
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string_keys = ["hello", "world", "hash", "table", "test"]
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print("Simple string hash (BAD - prone to collisions):")
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for key in string_keys:
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hash_val = string_hash_simple(key, table_size)
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print(f" h('{key}') = {hash_val}")
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print("\nPolynomial string hash (GOOD - better distribution):")
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for key in string_keys:
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hash_val = string_hash_polynomial(key, table_size)
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print(f" h('{key}') = {hash_val}")
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print()
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def demo_collision_comparison():
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"""Demonstrate collision behavior with different hash functions."""
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print("=" * 60)
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print("Collision Comparison Demonstration")
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print("=" * 60)
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# Generate test keys
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keys = list(range(100, 200))
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table_size = 50
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from src.hash_functions import (
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division_hash,
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multiplication_hash,
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string_hash_simple,
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string_hash_polynomial
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)
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hash_funcs = {
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'Division': division_hash,
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'Multiplication': lambda k, s: multiplication_hash(k, s),
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}
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print(f"\nTesting with {len(keys)} keys and table size {table_size}\n")
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for name, hash_func in hash_funcs.items():
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hash_values = [hash_func(k, table_size) for k in keys]
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collisions = len(keys) - len(set(hash_values))
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collision_rate = collisions / len(keys) * 100
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print(f"{name} method:")
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print(f" Collisions: {collisions}")
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print(f" Collision rate: {collision_rate:.2f}%")
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print(f" Buckets used: {len(set(hash_values))}/{table_size}")
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print()
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if __name__ == "__main__":
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demo_direct_address_table()
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demo_open_addressing()
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demo_separate_chaining()
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demo_hash_functions()
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demo_collision_comparison()
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