mirror of
https://github.com/prdlk/leetcode.git
synced 2026-11-02 13:12:44 +00:00
99 lines
2.8 KiB
Python
99 lines
2.8 KiB
Python
"""
|
|
380. Insert Delete GetRandom O(1)
|
|
Difficulty: Medium
|
|
https://leetcode.com/problems/insert-delete-getrandom-o1/
|
|
|
|
──────────────────────────────────────────────────
|
|
|
|
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.
|
|
|
|
You must implement the functions of the class such that each function
|
|
works in average O(1) time complexity.
|
|
|
|
|
|
|
|
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:
|
|
|
|
• -2^31 <= val <= 2^31 - 1
|
|
|
|
• At most 2 * 10^5 calls will be made to insert, remove, and
|
|
getRandom.
|
|
|
|
• There will be at least one element in the data structure when
|
|
getRandom is called.
|
|
"""
|
|
|
|
from random import choice
|
|
|
|
|
|
class RandomizedSet:
|
|
def __init__(self):
|
|
self.list = []
|
|
self.dict = {}
|
|
|
|
def insert(self, val: int) -> bool:
|
|
if val in self.dict:
|
|
return False
|
|
self.dict[val] = len(self.list)
|
|
self.list.append(val)
|
|
return True
|
|
|
|
def remove(self, val: int) -> bool:
|
|
if val in self.dict:
|
|
last, idx = self.list[-1], self.dict[val]
|
|
self.list[idx], self.dict[last] = last, idx
|
|
self.list.pop()
|
|
del self.dict[val]
|
|
return True
|
|
return False
|
|
|
|
def getRandom(self) -> int:
|
|
return choice(self.list)
|
|
|
|
|
|
# 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()
|