101 lines
2.8 KiB
Python
101 lines
2.8 KiB
Python
class HashTable:
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_DELETED = object()
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def __init__(self, capacity=10):
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if isinstance(capacity, bool) or not isinstance(capacity, int):
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raise TypeError("Capacity must be an integer")
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if capacity <= 0:
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raise ValueError("Capacity must be positive")
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self._capacity = capacity
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self._slots = [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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return self._capacity
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def hash(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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h = 0
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for char in key:
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h = (31 * h + ord(char)) % self.capacity
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return h
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def probe(self, key):
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start = self.hash(key)
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first_deleted = None
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for step in range(self.capacity):
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index = (start + step) % self.capacity
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slot = self._slots[index]
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if slot is None:
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return first_deleted if first_deleted is not None else index
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if slot is self._DELETED:
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if first_deleted is None:
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first_deleted = index
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elif slot[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 __setitem__(self, key, value):
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index = self.probe(key)
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slot = self._slots[index]
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if slot is not None and slot is not self._DELETED:
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self._slots[index] = (key, value)
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return
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if (self._size + 1) * 10 > self.capacity * 7:
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self._resize()
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index = self.probe(key)
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self._slots[index] = (key, value)
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self._size += 1
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def __getitem__(self, key):
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index = self.probe(key)
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slot = self._slots[index]
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if slot is None or slot is self._DELETED:
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raise KeyError(key)
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return slot[1]
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def __delitem__(self, key):
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index = self.probe(key)
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slot = self._slots[index]
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if slot is None or slot is self._DELETED:
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raise KeyError(key)
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self._slots[index] = self._DELETED
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self._size -= 1
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def __contains__(self, key):
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try:
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self[key]
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except KeyError:
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return False
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return True
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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 slot in self._slots:
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if slot is not None and slot is not self._DELETED:
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yield slot[0]
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def load_factor(self):
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return len(self) / self.capacity
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def _resize(self):
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old_slots = self._slots
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self._capacity *= 2
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self._slots = [None] * self.capacity
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for slot in old_slots:
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if slot is not None and slot is not self._DELETED:
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self._slots[self.probe(slot[0])] = slot
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