22.DesignaSearchIndexer.py

# Design a Search Indexer system that stores multiple text documents and 
# allows efficient keyword-based searching by building an inverted 
# index (mapping each word to the list of document IDs containing it). 
# The system should work entirely in-memory without any external database.

import re
from collections import defaultdict

class SearchIndexer:
    def __init__(self):
        self.documents = {}
        self.index = defaultdict(set)

    def add_document(self, doc_id: int, content: str):
        self.documents[doc_id] = content

    def build_index(self):
        for doc_id, text in self.documents.items():
            words = re.findall(r'\w+', text.lower())
            for word in words:
                self.index[word].add(doc_id)

    def search(self, keyword: str):
        keyword = keyword.lower()
        return list(self.index.get(keyword, []))
    
if __name__ == "__main__":
    s = SearchIndexer()
    s.add_document(1, "The cat sat on the mat")
    s.add_document(2, "The dog chased the cat")
    s.add_document(3, "The bird sang sweetly")

    s.build_index()

    print("Search Results for 'cat':", s.search("cat"))
    print("Search Results for 'dog':", s.search("dog"))
    print("Search Results for 'bird':", s.search("bird"))
    print("Search Results for 'lion':", s.search("lion"))