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119 lines
3.5 KiB
119 lines
3.5 KiB
"""
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File: hash_map_chaining.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 HashMapChaining:
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"""链式地址哈希表"""
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def __init__(self):
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"""构造方法"""
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self.size = 0 # 键值对数量
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self.capacity = 4 # 哈希表容量
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self.load_thres = 2.0 / 3.0 # 触发扩容的负载因子阈值
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self.extend_ratio = 2 # 扩容倍数
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self.buckets = [[] for _ in range(self.capacity)] # 桶数组
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def hash_func(self, key: int) -> int:
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"""哈希函数"""
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return key % self.capacity
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def load_factor(self) -> float:
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"""负载因子"""
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return self.size / self.capacity
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def get(self, key: int) -> str | None:
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"""查询操作"""
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index = self.hash_func(key)
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bucket = self.buckets[index]
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# 遍历桶，若找到 key ，则返回对应 val
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for pair in bucket:
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if pair.key == key:
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return pair.val
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# 若未找到 key ，则返回 None
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return None
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def put(self, key: int, val: str):
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"""添加操作"""
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# 当负载因子超过阈值时，执行扩容
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if self.load_factor() > self.load_thres:
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self.extend()
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index = self.hash_func(key)
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bucket = self.buckets[index]
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# 遍历桶，若遇到指定 key ，则更新对应 val 并返回
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for pair in bucket:
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if pair.key == key:
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pair.val = val
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return
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# 若无该 key ，则将键值对添加至尾部
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pair = Pair(key, val)
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bucket.append(pair)
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self.size += 1
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def remove(self, key: int):
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"""删除操作"""
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index = self.hash_func(key)
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bucket = self.buckets[index]
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# 遍历桶，从中删除键值对
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for pair in bucket:
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if pair.key == key:
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bucket.remove(pair)
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self.size -= 1
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break
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def extend(self):
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"""扩容哈希表"""
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# 暂存原哈希表
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buckets = self.buckets
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# 初始化扩容后的新哈希表
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self.capacity *= self.extend_ratio
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self.buckets = [[] for _ in range(self.capacity)]
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self.size = 0
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# 将键值对从原哈希表搬运至新哈希表
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for bucket in buckets:
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for pair in bucket:
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self.put(pair.key, pair.val)
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def print(self):
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"""打印哈希表"""
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for bucket in self.buckets:
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res = []
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for pair in bucket:
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res.append(str(pair.key) + " -> " + pair.val)
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print(res)
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"""Driver Code"""
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if __name__ == "__main__":
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# 初始化哈希表
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hashmap = HashMapChaining()
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# 添加操作
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# 在哈希表中添加键值对 (key, value)
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hashmap.put(12836, "小哈")
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hashmap.put(15937, "小啰")
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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, "小鸭")
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print("\n添加完成后，哈希表为\n[Key1 -> Value1, Key2 -> Value2, ...]")
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hashmap.print()
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# 查询操作
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# 向哈希表中输入键 key ，得到值 value
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name = hashmap.get(13276)
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print("\n输入学号 13276 ，查询到姓名 " + name)
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# 删除操作
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# 在哈希表中删除键值对 (key, value)
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hashmap.remove(12836)
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print("\n删除 12836 后，哈希表为\n[Key1 -> Value1, Key2 -> Value2, ...]")
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hashmap.print()
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