README.md

705. 设计哈希集合

English Version

题目描述

不使用任何内建的哈希表库设计一个哈希集合（HashSet）。

实现 MyHashSet 类：

• void add(key) 向哈希集合中插入值 key 。
• bool contains(key) 返回哈希集合中是否存在这个值 key 。
• void remove(key) 将给定值 key 从哈希集合中删除。如果哈希集合中没有这个值，什么也不做。

 

示例：

输入：
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
输出：
[null, null, null, true, false, null, true, null, false]

解释：
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(1);      // set = [1]
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(1); // 返回 True
myHashSet.contains(3); // 返回 False ，（未找到）
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(2); // 返回 True
myHashSet.remove(2);   // set = [1]
myHashSet.contains(2); // 返回 False ，（已移除）

 

提示：

• 0 <= key <= 106
• 最多调用 104 次 add、remove 和 contains 。

 

进阶：你可以不使用内建的哈希集合库解决此问题吗？

解法

数组实现。

Python3

class MyHashSet:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.data = [False] * 1000001

    def add(self, key: int) -> None:
        self.data[key] = True

    def remove(self, key: int) -> None:
        self.data[key] = False

    def contains(self, key: int) -> bool:
        """
        Returns true if this set contains the specified element
        """
        return self.data[key]



# Your MyHashSet object will be instantiated and called as such:
# obj = MyHashSet()
# obj.add(key)
# obj.remove(key)
# param_3 = obj.contains(key)

Java

• 可以一次性开辟一个大的数组，存放所有元素。

class MyHashSet {

    private boolean[] data;

    /** Initialize your data structure here. */
    public MyHashSet() {
        data = new boolean[1000001];
    }

    public void add(int key) {
        data[key] = true;
    }

    public void remove(int key) {
        data[key] = false;
    }

    /** Returns true if this set contains the specified element */
    public boolean contains(int key) {
        return data[key];
    }
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * MyHashSet obj = new MyHashSet();
 * obj.add(key);
 * obj.remove(key);
 * boolean param_3 = obj.contains(key);
 */

• 也可以开辟一个大小为 SIZE 的数组，数组的每个位置是一个链表。

class MyHashSet {

    private static final int SIZE = 1000;
    private LinkedList[] data;

    /** Initialize your data structure here. */
    public MyHashSet() {
        data = new LinkedList[SIZE];
        Arrays.fill(data, new LinkedList<Integer>());
    }

    public void add(int key) {
        int index = hash(key);
        Iterator<Integer> iterator = data[index].iterator();
        while (iterator.hasNext()) {
            Integer e = iterator.next();
            if (e == key) return;
        }
        data[index].addFirst(key);
    }

    public void remove(int key) {
        int index = hash(key);
        ListIterator<Integer> iterator = data[index].listIterator();
        while (iterator.hasNext()) {
            Integer e = iterator.next();
            if (e == key) iterator.remove();
        }
    }

    /** Returns true if this set contains the specified element */
    public boolean contains(int key) {
        int index = hash(key);
        Iterator<Integer> iterator = data[index].iterator();
        while (iterator.hasNext()) {
            Integer e = iterator.next();
            if (e == key) return true;
        }
        return false;
    }

    private int hash(int key) {
        return key % SIZE;
    }
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * MyHashSet obj = new MyHashSet();
 * obj.add(key);
 * obj.remove(key);
 * boolean param_3 = obj.contains(key);
 */

TypeScript

class MyHashSet {
    data: Array<boolean>;
    constructor() {
        this.data = new Array(10 ** 6 + 1).fill(false);
    }

    add(key: number): void {
        this.data[key] = true;
    }

    remove(key: number): void {
        this.data[key] = false;
    }

    contains(key: number): boolean {
        return this.data[key];
    }
}

/**
 * Your MyHashSet object will be instantiated and called as such:
 * var obj = new MyHashSet()
 * obj.add(key)
 * obj.remove(key)
 * var param_3 = obj.contains(key)
 */

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