105 lines
3.4 KiB
Python
105 lines
3.4 KiB
Python
class HashTable:
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_DELETED = object()
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def __init__(self, capacity=10):
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if type(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._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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return self._capacity
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def hash(self, key):
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if type(key) != str:
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raise TypeError
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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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if type(key) != str:
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raise TypeError
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start = self.hash(key)
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deleted = None
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for i in range(self.capacity):
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index = (start + i) % self.capacity
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item = self._table[index]
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if item is None:
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if deleted is not None:
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return deleted
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return index
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if item is self._DELETED:
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if deleted is None:
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deleted = index
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elif item[0] == key:
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return index
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if deleted is not None:
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return deleted
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raise RuntimeError
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def __setitem__(self, key, value):
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if type(key) != str:
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raise TypeError
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try:
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index = self.probe(key)
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item = self._table[index]
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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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except RuntimeError:
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pass
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if (self._size + 1) / self.capacity > 0.7:
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old_table = self._table
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self._capacity = self._capacity * 2
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self._table = [None] * self.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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index = self.probe(item[0])
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self._table[index] = item
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self._size += 1
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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 __getitem__(self, key):
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if type(key) != str:
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raise TypeError
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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:
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raise KeyError(key)
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return item[1]
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def __delitem__(self, key):
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if type(key) != str:
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raise TypeError
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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:
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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 type(key) != str:
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raise TypeError
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try:
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index = self.probe(key)
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item = self._table[index]
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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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return True
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return False
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except RuntimeError:
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return False
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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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keys = []
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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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keys.append(item[0])
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return iter(keys)
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def load_factor(self):
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return self._size / self.capacity
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