380. Insert Delete GetRandom O(1)

Difficulty: Medium
18 / 18 test cases passed.
Runtime: 556 ms
Memory Usage: 17.9 MB

Author: YuriSpiridonov

Medium/380.InsertDeleteGetRandomO(1).py

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+"""
+    Implement the RandomizedSet class:
+    - bool insert(int val) Inserts an item val into the set if not present. 
+      Returns true if the item was not present, false otherwise.
+    - bool remove(int val) Removes an item val from the set if present. 
+      Returns true if the item was present, false otherwise.
+    - int getRandom() Returns a random element from the current set of elements 
+      (it's guaranteed that at least one element exists when this method is 
+      called). Each element must have the same probability of being returned.
+
+    Follow up: Could you implement the functions of the class with each function 
+    works in average O(1) time?
+
+    Example:
+    Input
+    ["RandomizedSet", "insert", "remove", "insert", "getRandom", "remove", "insert", "getRandom"]
+    [[], [1], [2], [2], [], [1], [2], []]
+    Output
+    [null, true, false, true, 2, true, false, 2]
+    Explanation
+                RandomizedSet randomizedSet = new RandomizedSet();
+                randomizedSet.insert(1); // Inserts 1 to the set. Returns true 
+                                         // as 1 was inserted successfully.
+                randomizedSet.remove(2); // Returns false as 2 does not exist 
+                                         // in the set.
+                randomizedSet.insert(2); // Inserts 2 to the set, returns true. 
+                                         // Set now contains [1,2].
+                randomizedSet.getRandom(); // getRandom() should return either 
+                                           // 1 or 2 randomly.
+                randomizedSet.remove(1); // Removes 1 from the set, returns true.
+                                         // Set now contains [2].
+                randomizedSet.insert(2); // 2 was already in the set, so return 
+                                         // false.
+                randomizedSet.getRandom(); // Since 2 is the only number in the 
+                                           // set, getRandom() will always 
+                                           // return 2.
+
+    Constraints:
+        - -2**31 <= val <= 2**31 - 1
+        - At most 105 calls will be made to insert, remove, and getRandom.
+        - There will be at least one element in the data structure when 
+          getRandom is called.
+"""
+#Difficulty: Medium
+#18 / 18 test cases passed.
+#Runtime: 556 ms
+#Memory Usage: 17.9 MB
+
+#Runtime: 556 ms, faster than 8.03% of Python3 online submissions for Insert Delete GetRandom O(1).
+#Memory Usage: 17.9 MB, less than 62.45% of Python3 online submissions for Insert Delete GetRandom O(1).
+
+import random
+
+class RandomizedSet:
+
+    def __init__(self):
+        """
+        Initialize your data structure here.
+        """
+        self.set = []
+
+    def insert(self, val: int) -> bool:
+        """
+        Inserts a value to the set. Returns true if the set did not already 
+        contain the specified element.
+        """
+        if val not in self.set:
+            self.set.append(val)
+            return True
+        return False
+
+    def remove(self, val: int) -> bool:
+        """
+        Removes a value from the set. Returns true if the set contained the 
+        specified element.
+        """
+        if val in self.set:
+            self.set.remove(val)
+            return True
+        return False
+
+    def getRandom(self) -> int:
+        """
+        Get a random element from the set.
+        """
+        return random.choice(self.set)
+
+
+# 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()