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Problem solution · Python

Insert Delete Getrandom O1 Duplicates Allowed

Insert Delete Getrandom O1 Duplicates Allowed: a Python solution using hash-based lookup. Learn the idea, check the complexity, and read the full code, with credit to Kamyu LeetCode Solutions.

Technique
Hash-based lookup
Source
Kamyu LeetCode Solutions
Length
56 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Hash-based lookup

For Insert Delete Getrandom O1 Duplicates Allowed, the implementation stores previously seen values or frequencies in a hash table for direct membership and lookup operations.

  1. Decide the key that represents the information needed later.
  2. Update its count or stored state while scanning the input.
  3. Use constant-time expected lookups to detect matches or assemble the result.

Code notes

  • 56 lines of Python from the credited upstream file insert-delete-getrandom-o1-duplicates-allowed.py.
  • The implementation visibly relies on sequence storage, hash lookup.
  • No explicit loop blocks detected.

Complexity

Expected hash operations are constant time, but the surrounding scan and the number of stored keys determine total work and memory.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from Kamyu LeetCode Solutions by kamyu104 and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeInsert Delete Getrandom O1 Duplicates Allowed · PythonPython
Use this to learn the idea, then write your own version.
# Time:  O(1)# Space: O(n) from random import randintfrom collections import defaultdict class RandomizedCollection(object):     def __init__(self):        """        Initialize your data structure here.        """        self.__list = []        self.__used = defaultdict(list)      def insert(self, val):        """        Inserts a value to the collection. Returns true if the collection did not already contain the specified element.        :type val: int        :rtype: bool        """        has = val in self.__used         self.__list += (val, len(self.__used[val])),        self.__used[val] += len(self.__list)-1,         return not has      def remove(self, val):        """        Removes a value from the collection. Returns true if the collection contained the specified element.        :type val: int        :rtype: bool        """        if val not in self.__used:            return False         self.__used[self.__list[-1][0]][self.__list[-1][1]] = self.__used[val][-1]        self.__list[self.__used[val][-1]], self.__list[-1] = self.__list[-1], self.__list[self.__used[val][-1]]         self.__used[val].pop()        if not self.__used[val]:            self.__used.pop(val)        self.__list.pop()         return True     def getRandom(self):        """        Get a random element from the collection.        :rtype: int        """        return self.__list[randint(0, len(self.__list)-1)][0]

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