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139 lines
4.7 KiB
139 lines
4.7 KiB
"""
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File: hash_map_open_addressing.py
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Created Time: 2023-06-13
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Author: krahets (krahets@163.com)
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"""
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import sys
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from pathlib import Path
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sys.path.append(str(Path(__file__).parent.parent))
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from chapter_hashing.array_hash_map import Pair
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class HashMapOpenAddressing:
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"""開放定址雜湊表"""
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def __init__(self):
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"""建構子"""
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self.size = 0 # 鍵值對數量
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self.capacity = 4 # 雜湊表容量
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self.load_thres = 2.0 / 3.0 # 觸發擴容的負載因子閾值
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self.extend_ratio = 2 # 擴容倍數
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self.buckets: list[Pair | None] = [None] * self.capacity # 桶陣列
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self.TOMBSTONE = Pair(-1, "-1") # 刪除標記
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def hash_func(self, key: int) -> int:
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"""雜湊函式"""
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return key % self.capacity
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def load_factor(self) -> float:
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"""負載因子"""
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return self.size / self.capacity
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def find_bucket(self, key: int) -> int:
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"""搜尋 key 對應的桶索引"""
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index = self.hash_func(key)
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first_tombstone = -1
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# 線性探查，當遇到空桶時跳出
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while self.buckets[index] is not None:
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# 若遇到 key ，返回對應的桶索引
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if self.buckets[index].key == key:
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# 若之前遇到了刪除標記，則將鍵值對移動至該索引處
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if first_tombstone != -1:
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self.buckets[first_tombstone] = self.buckets[index]
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self.buckets[index] = self.TOMBSTONE
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return first_tombstone # 返回移動後的桶索引
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return index # 返回桶索引
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# 記錄遇到的首個刪除標記
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if first_tombstone == -1 and self.buckets[index] is self.TOMBSTONE:
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first_tombstone = index
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# 計算桶索引，越過尾部則返回頭部
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index = (index + 1) % self.capacity
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# 若 key 不存在，則返回新增點的索引
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return index if first_tombstone == -1 else first_tombstone
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def get(self, key: int) -> str:
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"""查詢操作"""
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# 搜尋 key 對應的桶索引
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index = self.find_bucket(key)
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# 若找到鍵值對，則返回對應 val
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if self.buckets[index] not in [None, self.TOMBSTONE]:
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return self.buckets[index].val
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# 若鍵值對不存在，則返回 None
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return None
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def put(self, key: int, val: str):
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"""新增操作"""
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# 當負載因子超過閾值時，執行擴容
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if self.load_factor() > self.load_thres:
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self.extend()
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# 搜尋 key 對應的桶索引
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index = self.find_bucket(key)
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# 若找到鍵值對，則覆蓋 val 並返回
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if self.buckets[index] not in [None, self.TOMBSTONE]:
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self.buckets[index].val = val
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return
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# 若鍵值對不存在，則新增該鍵值對
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self.buckets[index] = Pair(key, val)
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self.size += 1
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def remove(self, key: int):
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"""刪除操作"""
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# 搜尋 key 對應的桶索引
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index = self.find_bucket(key)
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# 若找到鍵值對，則用刪除標記覆蓋它
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if self.buckets[index] not in [None, self.TOMBSTONE]:
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self.buckets[index] = self.TOMBSTONE
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self.size -= 1
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def extend(self):
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"""擴容雜湊表"""
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# 暫存原雜湊表
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buckets_tmp = self.buckets
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# 初始化擴容後的新雜湊表
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self.capacity *= self.extend_ratio
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self.buckets = [None] * self.capacity
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self.size = 0
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# 將鍵值對從原雜湊表搬運至新雜湊表
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for pair in buckets_tmp:
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if pair not in [None, self.TOMBSTONE]:
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self.put(pair.key, pair.val)
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def print(self):
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"""列印雜湊表"""
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for pair in self.buckets:
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if pair is None:
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print("None")
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elif pair is self.TOMBSTONE:
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print("TOMBSTONE")
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else:
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print(pair.key, "->", pair.val)
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"""Driver Code"""
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if __name__ == "__main__":
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# 初始化雜湊表
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hashmap = HashMapOpenAddressing()
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# 新增操作
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# 在雜湊表中新增鍵值對 (key, val)
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hashmap.put(12836, "小哈")
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hashmap.put(15937, "小囉")
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hashmap.put(16750, "小算")
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hashmap.put(13276, "小法")
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hashmap.put(10583, "小鴨")
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print("\n新增完成後，雜湊表為\nKey -> Value")
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hashmap.print()
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# 查詢操作
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# 向雜湊表中輸入鍵 key ，得到值 val
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name = hashmap.get(13276)
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print("\n輸入學號 13276 ，查詢到姓名 " + name)
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# 刪除操作
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# 在雜湊表中刪除鍵值對 (key, val)
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hashmap.remove(16750)
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print("\n刪除 16750 後，雜湊表為\nKey -> Value")
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hashmap.print()
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