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Implement the RandomizedSet
class:
RandomizedSet()
Initializes the RandomizedSet
object.
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.
Example 1:
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:
-231 <= val <= 231 - 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.
Follow up: Could you implement the functions of the class with each function works in
average O(1)
time?
[Design]
[Array]
[Hash Table]
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