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69 lines
2.5 KiB
Plaintext
69 lines
2.5 KiB
Plaintext
---
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title: '380. Insert Delete GetRandom O(1)'
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description: 'Implement the RandomizedSet class:'
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icon: dot
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topics:
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- { name: "Array", slug: "array" }
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- { name: "Hash Table", slug: "hash-table" }
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- { name: "Math", slug: "math" }
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- { name: "Design", slug: "design" }
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- { name: "Randomized", slug: "randomized" }
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issue: "https://github.com/prdlk/leetcode/issues/90"
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sidebar:
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label: 'Insert Delete GetRandom O(1)'
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badge: 'Medium'
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---
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::::warning
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You must implement the functions of the class such that each function works in average O(1) time complexity.
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::::
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### Example 1:
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- Input: ``
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- Output: ``
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- Explanation: 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`.
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### Constraints:
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- `-2^31 <= val <= 2^31 - 1`
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- At most 2 * 10^5 calls will be made to insert, remove, and getRandom.
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- There will be at least one element in the data structure when getRandom is called.
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## Solution
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```py
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from random import choice
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class RandomizedSet:
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def __init__(self):
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self.list = []
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self.dict = {}
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def insert(self, val: int) -> bool:
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if val in self.dict:
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return False
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self.dict[val] = len(self.list)
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self.list.append(val)
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return True
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def remove(self, val: int) -> bool:
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if val in self.dict:
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last, idx = self.list[-1], self.dict[val]
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self.list[idx], self.dict[last] = last, idx
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self.list.pop()
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del self.dict[val]
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return True
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return False
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def getRandom(self) -> int:
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return choice(self.list)
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# Your RandomizedSet object will be instantiated and called as such:
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# obj = RandomizedSet()
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# param_1 = obj.insert(val)
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# param_2 = obj.remove(val)
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# param_3 = obj.getRandom()
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```
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