Design a data structure that supports all following operations in average O(1) time.
insert(val): Inserts an item val to the set if not already present.
remove(val): Removes an item val from the set if present.
getRandom: Returns a random element from current set of elements. Each element must have the same probability of being returned.
Example:
// Init an empty set.
RandomizedSet randomSet = new RandomizedSet();
// Inserts 1 to the set. Returns true as 1 was inserted successfully.
randomSet.insert(1);
// Returns false as 2 does not exist in the set.
randomSet.remove(2);
// Inserts 2 to the set, returns true. Set now contains [1,2].
randomSet.insert(2);
// getRandom should return either 1 or 2 randomly.
randomSet.getRandom();
// Removes 1 from the set, returns true. Set now contains [2].
randomSet.remove(1);
// 2 was already in the set, so return false.
randomSet.insert(2);
// Since 2 is the only number in the set, getRandom always return 2.
randomSet.getRandom();
class RandomizedSet:
 
     def __init__(self):
         """
         Initialize your data structure here.
         """
         self.dic = {}
         self.l = []
 
     def insert(self, val):
         """
         Inserts a value to the set. Returns true if the set did not already contain the specified element.
         :type val: int
         :rtype: bool
         """
         if val in self.dic:
             return False
         self.l.append(val)
         self.dic[val] = len(self.l) - 1
         return True
         
 
     def remove(self, val):
         """
         Removes a value from the set. Returns true if the set contained the specified element.
         :type val: int
         :rtype: bool
         """
         if val not in self.dic:
             return False
         self.dic[self.l[-1]] = self.dic[val]
         self.l[self.dic[val]], self.l[-1] = self.l[-1], self.l[self.dic[val]]
         self.l.pop()
         del self.dic[val]
         return True
 
     def getRandom(self):
         """
         Get a random element from the set.
         :rtype: int
         """
         return random.choice(self.l)
 
 
 # Your RandomizedSet object will be instantiated and called as such:
 # obj = RandomizedSet()
 # param_1 = obj.insert(val)
 # param_2 = obj.remove(val)
 # param_3 = obj.getRandom()

class RandomizedSet:
 
     def __init__(self):
         """
         Initialize your data structure here.
         """
         self.dic = {}
         self.l = []
 
     def insert(self, val):
         """
         Inserts a value to the set. Returns true if the set did not already contain the specified element.
         :type val: int
         :rtype: bool
         """
         if val in self.dic:
             return False
         self.l.append(val)
         self.dic[val] = len(self.l) - 1
         return True
         
 
     def remove(self, val):
         """
         Removes a value from the set. Returns true if the set contained the specified element.
         :type val: int
         :rtype: bool
         """
         if val not in self.dic:
             return False
         self.dic[self.l[-1]] = self.dic[val]
         self.l[self.dic[val]], self.l[-1] = self.l[-1], self.l[self.dic[val]]
         self.l.pop()
         del self.dic[val]
         return True
 
     def getRandom(self):
         """
         Get a random element from the set.
         :rtype: int
         """
         return random.choice(self.l)
 
 
 # Your RandomizedSet object will be instantiated and called as such:
 # obj = RandomizedSet()
 # param_1 = obj.insert(val)
 # param_2 = obj.remove(val)
 # param_3 = obj.getRandom()
