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* Add the intial translation of code of all the languages * test * revert * Remove * Add Python and Java code for EN version
119 lines
3.7 KiB
Python
119 lines
3.7 KiB
Python
"""
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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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"""Chained address hash table"""
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def __init__(self):
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"""Constructor"""
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self.size = 0 # Number of key-value pairs
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self.capacity = 4 # Hash table capacity
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self.load_thres = 2.0 / 3.0 # Load factor threshold for triggering expansion
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self.extend_ratio = 2 # Expansion multiplier
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self.buckets = [[] for _ in range(self.capacity)] # Bucket array
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def hash_func(self, key: int) -> int:
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"""Hash function"""
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return key % self.capacity
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def load_factor(self) -> float:
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"""Load factor"""
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return self.size / self.capacity
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def get(self, key: int) -> str | None:
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"""Query operation"""
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index = self.hash_func(key)
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bucket = self.buckets[index]
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# Traverse the bucket, if the key is found, return the corresponding 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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# If the key is not found, return None
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return None
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def put(self, key: int, val: str):
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"""Add operation"""
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# When the load factor exceeds the threshold, perform expansion
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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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# Traverse the bucket, if the specified key is encountered, update the corresponding val and return
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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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# If the key is not found, add the key-value pair to the end
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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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"""Remove operation"""
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index = self.hash_func(key)
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bucket = self.buckets[index]
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# Traverse the bucket, remove the key-value pair from it
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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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"""Extend hash table"""
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# Temporarily store the original hash table
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buckets = self.buckets
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# Initialize the extended new hash table
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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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# Move key-value pairs from the original hash table to the new hash table
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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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"""Print hash table"""
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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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# Initialize hash table
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hashmap = HashMapChaining()
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# Add operation
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# Add key-value pair (key, value) to the hash table
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hashmap.put(12836, "Ha")
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hashmap.put(15937, "Luo")
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hashmap.put(16750, "Suan")
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hashmap.put(13276, "Fa")
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hashmap.put(10583, "Ya")
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print("\nAfter adding, the hash table is\n[Key1 -> Value1, Key2 -> Value2, ...]")
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hashmap.print()
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# Query operation
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# Enter key to the hash table, get value
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name = hashmap.get(13276)
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print("\nEnter student ID 13276, found name " + name)
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# Remove operation
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# Remove key-value pair (key, value) from the hash table
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hashmap.remove(12836)
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print("\nAfter removing 12836, the hash table is\n[Key1 -> Value1, Key2 -> Value2, ...]")
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hashmap.print()
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