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描述
Design a HashSet without using any built-in hash table libraries.
Implement MyHashSet class:
- void add(key) Inserts the value key into the HashSet.
- bool contains(key) Returns whether the value key exists in the HashSet or not.
- void remove(key) Removes the value key in the HashSet. If key does not exist in the HashSet, do nothing.
Example 1:
Input
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
Output
[null, null, null, true, false, null, true, null, false]
Explanation
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(1); // set = [1]
myHashSet.add(2); // set = [1, 2]
myHashSet.contains(1); // return True
myHashSet.contains(3); // return False, (not found)
myHashSet.add(2); // set = [1, 2]
myHashSet.contains(2); // return True
myHashSet.remove(2); // set = [1]
myHashSet.contains(2); // return False, (already removed)
Note:
0 <= key <= 10^6
At most 104 calls will be made to add, remove, and contains.
解析
根据题意，就是实现一个 Hashset ，直接使用列表的相关操作即可实现，很简单，不再赘述。这种方法使用了内置函数，不推荐使用。
解答
class MyHashSet(object):
def __init__(self):
"""
Initialize your data structure here.
"""
self.l = []
def add(self, key):
"""
:type key: int
:rtype: None
"""
if key not in self.l:
self.l.append(key)
def remove(self, key):
"""
:type key: int
:rtype: None
"""
if key in self.l:
self.l.remove(key)
def contains(self, key):
"""
Returns true if this set contains the specified element
:type key: int
:rtype: bool
"""
if key in self.l:
return True
return False
运行结果
Runtime: 1104 ms, faster than 25.11% of Python online submissions for Design HashSet.
Memory Usage: 18.3 MB, less than 85.65% of Python online submissions for Design HashSet.
解析
另外一种思路就是初始化一个数组，因为上面限制了 key 的长度在 10^6 之内，所以数组的长度设置成 1000001 ，全部都设置为 False ，如果有数字就设置为 True ，利用数组的基本操作完成题目中的各个函数功能。
解答
class MyHashSet(object):
def __init__(self):
"""
Initialize your data structure here.
"""
self.set = [False] * 1000001
def add(self, key):
"""
:type key: int
:rtype: None
"""
self.set[key] = True
def remove(self, key):
"""
:type key: int
:rtype: None
"""
self.set[key] = False
def contains(self, key):
"""
Returns true if this set contains the specified element
:type key: int
:rtype: bool
"""
return self.set[key]
运行结果
Runtime: 356 ms, faster than 35.60% of Python online submissions for Design HashSet.
Memory Usage: 41.2 MB, less than 5.18% of Python online submissions for Design HashSet.
原题链接：leetcode.com/problems/de…
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