147 lines
4.2 KiB
Python
147 lines
4.2 KiB
Python
class HashTable:
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_DELETED = object()
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def __init__(self, capacity=10):
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"""Vytvor prázdnu tabuľku s kladnou celočíselnou kapacitou."""
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if type(capacity) is not int:
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raise TypeError("It's not integer")
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if capacity <= 0:
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raise ValueError("Capacity > 0")
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self._capacity = capacity
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self._table = [None] * capacity
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self._size = 0
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@property
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def capacity(self):
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"""Vráť aktuálny počet pozícií v poli."""
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return self._capacity
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def hash(self, key):
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"""Vráť polynomiálny hash kľúča modulo aktuálna kapacita."""
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if not isinstance(key, str):
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raise TypeError("Key must be a string")
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h = 0
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for znak in key:
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h = (31 * h + ord(znak)) % self.capacity
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return h
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def probe(self, key):
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"""Vráť index kľúča alebo miesta na vloženie bez zmeny tabuľky."""
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if not isinstance(key, str):
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raise TypeError("Key must be a string")
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start = self.hash(key)
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first_deleted = None
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for krok in range(self.capacity):
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index = (start + krok) % self.capacity
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item = self._table[index]
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if item is None:
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if first_deleted is not None:
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return first_deleted
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return index
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if item is self._DELETED:
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if first_deleted is None:
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first_deleted = index
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elif item[0] == key:
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return index
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if first_deleted is not None:
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return first_deleted
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raise RuntimeError("Hash table is full")
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def load_factor(self):
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"""Vráť podiel počtu aktívnych položiek a kapacity."""
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return self._size / self.capacity
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def __getitem__(self, key):
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if not isinstance(key, str):
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raise TypeError("Key must be a string")
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index = self.probe(key)
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item = self._table[index]
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if item is None or item is self._DELETED or item[0] != key:
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raise KeyError(key)
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return item[1]
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def __setitem__(self, key, value):
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if not isinstance(key, str):
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raise TypeError("Key must be a string")
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index = self.probe(key)
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item = self._table[index]
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# Ak kľúč existuje, prepíš iba jeho hodnotu.
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if item is not None and item is not self._DELETED:
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if item[0] == key:
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self._table[index] = (key, value)
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return
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# Ak nový kľúč prekročí zaplnenie 0.7, zväčši tabuľku.
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if (self._size + 1) / self.capacity > 0.7:
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self._resize(self.capacity * 2)
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index = self.probe(key)
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self._table[index] = (key, value)
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self._size += 1
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def __delitem__(self, key):
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if not isinstance(key, str):
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raise TypeError("Key must be a string")
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index = self.probe(key)
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item = self._table[index]
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if item is None or item is self._DELETED or item[0] != key:
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raise KeyError(key)
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self._table[index] = self._DELETED
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self._size -= 1
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def __contains__(self, key):
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if not isinstance(key, str):
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raise TypeError("Key must be a string")
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try:
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index = self.probe(key)
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except RuntimeError:
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return False
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item = self._table[index]
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return (
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item is not None
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and item is not self._DELETED
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and item[0] == key
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)
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def __len__(self):
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return self._size
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def __iter__(self):
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for item in self._table:
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if item is not None and item is not self._DELETED:
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yield item[0]
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def _resize(self, new_capacity):
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"""Zväčši tabuľku a vlož všetky aktívne položky nanovo."""
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old_table = self._table
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self._capacity = new_capacity
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self._table = [None] * new_capacity
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self._size = 0
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for item in old_table:
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if item is not None and item is not self._DELETED:
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key, value = item
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index = self.probe(key)
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self._table[index] = (key, value)
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self._size += 1 |