committed from zkp

pythonkd · pythonkd · commit 22427fbeec83 · 2019-01-23T20:07:28.000+08:00
diff --git a/Introduction to algorithms/Dict.py b/Introduction to algorithms/Dict.py
@@ -0,0 +1,156 @@
+# -*- coding: utf-8 -*-
+class Array(object):
+
+    def __init__(self, size=16, init=None):
+        self.size = size
+        self._items = [init] * size
+
+    def __len__(self):
+        return self.size
+
+    def __setitem__(self, index, value):
+        self._items[index] = value
+
+    def __getitem__(self, index):
+        return self._items[index]
+
+    def __iter__(self):
+        for item in self._items:
+            yield item
+
+    def clear(self, init=None):
+        for i in len(self):
+            self._items[i] = init
+
+
+class Slot(object):
+
+    def __init__(self, key, value):
+        self.key, self.value = key, value
+
+
+class HashTable(object):
+    UNUSED = None
+    EMPTY = Slot(None, None)
+
+    def __init__(self):
+        self._table = Array(8, HashTable.UNUSED)
+        self.length = 0
+
+    def __len__(self):
+        return self.length
+
+    @property
+    def _loadfactor(self):
+        return self.length / float(len(self._table))
+
+    def _hash(self, key):
+        return abs(hash(key)) % len(self._table)
+
+    def slot_can_insert(self, index):
+        return self._table[index] is HashTable.UNUSED or self._table[index] is HashTable.EMPTY
+
+    def find_slot_for_insert(self, key):
+        index = self._hash(key)
+        _len = len(self._table)
+        while not self.slot_can_insert(index):
+            index = (index * 5 + 1) % _len
+        return index
+
+    def find_key(self, key):
+        index = self._hash(key)
+        _len = len(self._table)
+        while self._table[index] is not HashTable.UNUSED:
+            if self._table[index] is not HashTable.EMPTY and self._table[index].key == key:
+                return index
+            index = (index * 5 + 1) % _len
+        return None
+
+    def __contains__(self, key):
+        return self.find_key(key) is not None
+
+    def add(self, key, value):
+        if key in self:
+            index = self.find_key(key)
+            self._table[index].value = value
+            return False
+        else:
+            index = self.find_slot_for_insert(key)
+            self._table[index] = Slot(key, value)
+            self.length += 1
+            if self._loadfactor >= 0.8:
+                self._rehash()
+            return True
+
+    def _rehash(self):
+        old_table = self._table
+        new_size = len(self._table) * 2
+        self._table = Array(new_size, HashTable.UNUSED)
+        self.length = 0
+        for slot in old_table:
+            if slot is not HashTable.UNUSED and slot is not HashTable.EMPTY:
+                key = slot.key
+                index = self.find_slot_for_insert(key)
+                self._table[index] = slot
+                self.length += 1
+
+    def get(self, key, default=None):
+        index = self.find_key(key)
+        if index is not None:
+            return self._table[index].value
+        else:
+            return default
+
+    def remove(self, key):
+        index = self.find_key(key)
+        if index is None:
+            raise KeyError()
+        value = self._table[index].value
+        self._table[index] = HashTable.EMPTY
+        self.length -= 1
+        return value
+
+    def __iter__(self):
+        for slot in self._table:
+            if slot is not HashTable.UNUSED and slot is not HashTable.EMPTY:
+                yield slot.key
+
+
+class Dict(HashTable):
+    def _iter_slot(self):
+        for slot in self._table:
+            if slot is not HashTable.UNUSED and slot is not HashTable.EMPTY:
+                yield slot
+
+    def __setitem__(self, key, value):
+        self.add(key, value)
+
+    def __getitem__(self, key):
+       if key not in self:
+           raise KeyError()
+       else:
+           return self.get(key)
+
+    def items(self):
+        for slot in self._iter_slot():
+            yield(slot.key, slot.value)
+
+    def keys(self):
+        for slot in self._iter_slot():
+            yield slot.key
+
+    def values(self):
+        for slot in self._iter_slot():
+            yield slot.value
+
+def test_dict():
+    d = Dict()
+    d['a'] = 0
+    d['b'] = 1
+    d['c'] = 2
+    assert d['a'] == 0
+    assert sorted(list(d.keys())) == ['a', 'b', 'c']
+    assert sorted(list(d.values())) == [0,1,2]
+
+if __name__ == "__main__":
+    test_dict()
