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简单
设计
数组
哈希表
链表
哈希函数

English Version

题目描述

不使用任何内建的哈希表库设计一个哈希映射(HashMap)。

实现 MyHashMap 类:

  • MyHashMap() 用空映射初始化对象
  • void put(int key, int value) 向 HashMap 插入一个键值对 (key, value) 。如果 key 已经存在于映射中,则更新其对应的值 value
  • int get(int key) 返回特定的 key 所映射的 value ;如果映射中不包含 key 的映射,返回 -1
  • void remove(key) 如果映射中存在 key 的映射,则移除 key 和它所对应的 value

 

示例:

输入:
["MyHashMap", "put", "put", "get", "get", "put", "get", "remove", "get"]
[[], [1, 1], [2, 2], [1], [3], [2, 1], [2], [2], [2]]
输出:
[null, null, null, 1, -1, null, 1, null, -1]

解释:
MyHashMap myHashMap = new MyHashMap();
myHashMap.put(1, 1); // myHashMap 现在为 [[1,1]]
myHashMap.put(2, 2); // myHashMap 现在为 [[1,1], [2,2]]
myHashMap.get(1);    // 返回 1 ,myHashMap 现在为 [[1,1], [2,2]]
myHashMap.get(3);    // 返回 -1(未找到),myHashMap 现在为 [[1,1], [2,2]]
myHashMap.put(2, 1); // myHashMap 现在为 [[1,1], [2,1]](更新已有的值)
myHashMap.get(2);    // 返回 1 ,myHashMap 现在为 [[1,1], [2,1]]
myHashMap.remove(2); // 删除键为 2 的数据,myHashMap 现在为 [[1,1]]
myHashMap.get(2);    // 返回 -1(未找到),myHashMap 现在为 [[1,1]]

 

提示:

  • 0 <= key, value <= 106
  • 最多调用 104putgetremove 方法

解法

方法一:静态数组实现

直接创建一个大小为 $1000001$ 的数组,初始时数组中的每个元素都为 $-1$,表示哈希表中不存在该键值对。

调用 put 方法时,将数组中对应的位置赋值为 value;调用 get 方法时,返回数组中对应的位置的值;调用 remove 方法时,将数组中对应的位置赋值为 $-1$

以上操作,时间复杂度均为 $O(1)$

Python3

class MyHashMap:
    def __init__(self):
        self.data = [-1] * 1000001

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

    def get(self, key: int) -> int:
        return self.data[key]

    def remove(self, key: int) -> None:
        self.data[key] = -1


# Your MyHashMap object will be instantiated and called as such:
# obj = MyHashMap()
# obj.put(key,value)
# param_2 = obj.get(key)
# obj.remove(key)

Java

class MyHashMap {
    private int[] data = new int[1000001];

    public MyHashMap() {
        Arrays.fill(data, -1);
    }

    public void put(int key, int value) {
        data[key] = value;
    }

    public int get(int key) {
        return data[key];
    }

    public void remove(int key) {
        data[key] = -1;
    }
}

/**
 * Your MyHashMap object will be instantiated and called as such:
 * MyHashMap obj = new MyHashMap();
 * obj.put(key,value);
 * int param_2 = obj.get(key);
 * obj.remove(key);
 */

C++

class MyHashMap {
public:
    int data[1000001];

    MyHashMap() {
        memset(data, -1, sizeof data);
    }

    void put(int key, int value) {
        data[key] = value;
    }

    int get(int key) {
        return data[key];
    }

    void remove(int key) {
        data[key] = -1;
    }
};

/**
 * Your MyHashMap object will be instantiated and called as such:
 * MyHashMap* obj = new MyHashMap();
 * obj->put(key,value);
 * int param_2 = obj->get(key);
 * obj->remove(key);
 */

Go

type MyHashMap struct {
	data []int
}

func Constructor() MyHashMap {
	data := make([]int, 1000010)
	for i := range data {
		data[i] = -1
	}
	return MyHashMap{data}
}

func (this *MyHashMap) Put(key int, value int) {
	this.data[key] = value
}

func (this *MyHashMap) Get(key int) int {
	return this.data[key]
}

func (this *MyHashMap) Remove(key int) {
	this.data[key] = -1
}

/**
 * Your MyHashMap object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Put(key,value);
 * param_2 := obj.Get(key);
 * obj.Remove(key);
 */

TypeScript

class MyHashMap {
    data: Array<number>;
    constructor() {
        this.data = new Array(10 ** 6 + 1).fill(-1);
    }

    put(key: number, value: number): void {
        this.data[key] = value;
    }

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

    remove(key: number): void {
        this.data[key] = -1;
    }
}

/**
 * Your MyHashMap object will be instantiated and called as such:
 * var obj = new MyHashMap()
 * obj.put(key,value)
 * var param_2 = obj.get(key)
 * obj.remove(key)
 */