Insert Delete GetRandom O(1)

Insert-Delete-GetRandom-O(1).py

import random

class RandomizedSet:
    
    """
        set = { 1: 0, 2: 1 }
        indexes = { 0: 1, 1: 2}
    """
    
    def __init__(self):
        self.set = {}
        self.indexes = {}
        self.index = 0

    def insert(self, val: int) -> bool:
        if val in self.set:
            return False
        
        self.set[val] = self.index
        self.indexes[self.index] = val
        self.index += 1
        
        return True

    def remove(self, val: int) -> bool:
        if val in self.set:
            self.index -= 1
            index = self.set[val]
            lastValue = self.indexes[self.index]
            
            self.indexes[index] = lastValue
            self.set[lastValue] = index
            
            del self.set[val]
            del self.indexes[self.index]
            
            return True
            
        return False

    def getRandom(self) -> int:
        length = len(self.set)
        
        if length > 0:
            randIndex = random.randrange(length)
            
            return self.indexes[randIndex]
        
        return None