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class TsNode(object): |
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key = None |
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value = None |
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left = None |
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mid = None |
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right = None |
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def __init__(self, key, value=None, left=None, right=None, mid=None): |
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self.key = key |
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if value is not None: |
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self.value = value |
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if left is not None: |
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self.left = left |
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if right is not None: |
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self.right = right |
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if mid is not None: |
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self.mid = mid |
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def char_at(text, i): |
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if len(text) - 1 < i: |
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return -1 |
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return ord(text[i]) |
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class TernarySearchTrie(object): |
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root = None |
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N = 0 |
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def put(self, key, value): |
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self.root = self._put(self.root, key, value, 0) |
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def _put(self, x, key, value, d): |
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c = char_at(key, d) |
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if x is None: |
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x = TsNode(key=c) |
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compared = c - x.key |
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if compared < 0: |
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x.left = self._put(x.left, key, value, d) |
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elif compared > 0: |
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x.right = self._put(x.right, key, value, d) |
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else: |
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if len(key)-1 == d: |
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if x.value is None: |
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self.N += 1 |
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x.value = value |
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else: |
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x.mid = self._put(x.mid, key, value, d + 1) |
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return x |
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def get(self, key): |
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x = self._get(self.root, key, 0) |
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if x is not None: |
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return x.value |
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return None |
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def _get(self, x, key, d): |
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c = char_at(key, d) |
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if x is None: |
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return None |
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compared = c - x.key |
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if compared < 0: |
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return self._get(x.left, key, d) |
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elif compared > 0: |
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return self._get(x.right, key, d) |
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else: |
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if len(key) - 1 == d: |
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return x |
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else: |
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return self._get(x.mid, key, d + 1) |
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def size(self): |
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return self.N |
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def is_empty(self): |
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return self.N == 0 |
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def contains_key(self, key): |
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x = self._get(self.root, key, 0) |
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if x is None: |
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return False |
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return x.value is not None |
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def delete(self, key): |
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x = self._get(self.root, key, 0) |
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if x is not None: |
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self.N -= 1 |
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x.value = None |
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def values(self): |
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queue = [] |
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self._collect_values(self.root, "", queue) |
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return queue |
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def keys(self): |
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queue = [] |
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self._collect(self.root, "", queue) |
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return queue |
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def _collect(self, x, prefix, queue): |
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if x is None: |
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return |
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if x.value is not None: |
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queue.append(prefix + chr(x.key)) |
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self._collect(x.left, prefix, queue) |
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self._collect(x.mid, prefix + chr(x.key), queue) |
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self._collect(x.right, prefix, queue) |
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def _collect_values(self, x, prefix, queue): |
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if x is None: |
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return |
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if x.value is not None: |
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queue.append(x.value) |
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self._collect(x.left, prefix, queue) |
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self._collect(x.mid, prefix + chr(x.key), queue) |
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self._collect(x.right, prefix, queue) |