TikTok Interview: Design Randomized Set O(1)

Classic data structure design question in TikTok interviews. This article demonstrates how to achieve O(1) insertion, deletion, search, and random access. oavoservice helps you master advanced data structure design.

📋 Problem Reconstruction

Design a RandomizedSet supporting the following operations with average O(1) time complexity:

1. insert(val) - Insert element, return true if not present.
2. remove(val) - Remove element, return true if present.
3. search(val) - Check if element exists.
4. getRandom() - Return a random element.

Constraint: Probability of each element being returned must be equal.

🎯 Core Challenges

1. O(1) Insert/Delete - Fast location required
2. O(1) Random Access - Index access needed
3. Equal Probability - Ensure fairness
4. Space Efficiency - Minimize overhead

💡 Solution Strategy (oavoservice Approach)

Method: Array + Hash Map

import random

class RandomizedSet:
    def __init__(self):
        self.data = []  # Store elements for random access
        self.index_map = {}  # {val: index} for O(1) lookup
    
    def insert(self, val):
        if val in self.index_map:
            return False
        
        self.index_map[val] = len(self.data)
        self.data.append(val)
        return True
    
    def remove(self, val):
        if val not in self.index_map:
            return False
        
        # Swap with last element to delete in O(1)
        last_element = self.data[-1]
        idx_to_remove = self.index_map[val]
        
        self.data[idx_to_remove] = last_element
        self.index_map[last_element] = idx_to_remove
        
        self.data.pop()
        del self.index_map[val]
        return True
    
    def getRandom(self):
        return random.choice(self.data)

🚀 Deep Follow-ups

Q1: Why use swap for deletion?

oavoservice Explanation:

• Removing from middle of array is O(n).
• Swapping with last element allows O(1) pop.
• Does not affect randomness as order doesn't matter.

Q2: How to ensure uniform distribution?

oavoservice Explanation:

• random.choice() uses uniform distribution.
• Key is maintaining a contiguous array.

Q3: What if duplicate elements are allowed?

oavoservice Suggestion:

• Use index_map storing set of indices: {val: {idx1, idx2}}.
• RandomizedCollection variation.

💼 How oavoservice Helps with TikTok Interviews

Multiple Solutions - Basic to advanced Trade-off Analysis - Pros/cons comparison Extension Discussion - Duplicates, weighted variants Code Optimization - Efficient implementation

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Tags: #TikTok #DataStructure #RandomizedSet #HashMap #VOHelp #InterviewPrep #1point3acres

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