380 - Insert Delete Getrandom O1
Written on November 12, 2017
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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.
import random
class RandomizedSet:
def __init__(self):
"""
Initialize your data structure here.
"""
self.nums = []
self.index_map = {}
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.index_map:
self.nums.append(val)
self.index_map[val] = len(self.nums) - 1
return True
else:
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.index_map:
index, last = self.index_map[val], self.nums[-1]
self.index_map[last], self.nums[index] = index, last
self.nums.pop()
del self.index_map[val]
return True
else:
return False
def getRandom(self) -> int:
"""
Get a random element from the set.
"""
return random.choice(self.nums)