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LeetCode: 706. 设计哈希映射

1、题目描述

不使用任何内建的哈希表库设计一个哈希映射

具体地说,你的设计应该包含以下的功能

put(key, value):向哈希映射中插入(键,值)的数值对。如果键对应的值已经存在,更新这个值。 get(key):返回给定的键所对应的值,如果映射中不包含这个键,返回-1。 remove(key):如果映射中存在这个键,删除这个数值对。

示例:

MyHashMap hashMap = new MyHashMap();
hashMap.put(1, 1);          
hashMap.put(2, 2);         
hashMap.get(1);            // 返回 1
hashMap.get(3);            // 返回 -1 (未找到)
hashMap.put(2, 1);         // 更新已有的值
hashMap.get(2);            // 返回 1 
hashMap.remove(2);         // 删除键为2的数据
hashMap.get(2);            // 返回 -1 (未找到) 

注意:

  • 所有的值都在 [1, 1000000]的范围内。

  • 操作的总数目在[1, 10000]范围内。

  • 不要使用内建的哈希库。

2、解题思路

class Node:
    def __init__(self, existed, key, val, next_node):
        self.existed = existed
        self.key = key
        self.val = val
        self.next_node = next_node


class MyHashMap:

    def __init__(self):
        """
        Initialize your data structure here.
        """

        self.capacity = 100000
        self.pool = [Node(False, None, None, None) for _ in range(self.capacity)]

    def put(self, key: int, value: int) -> None:
        """
        value will always be non-negative.
        """

        hash = key % self.capacity

        if self.pool[hash].existed:
            temp = self.pool[hash]
            while temp.next_node:
                if temp.key == key:
                    temp.val = value
                    return
            if temp.key == key:
                temp.val = value
            else:
                temp.next_node = Node(True, key, value, None)
            return

        else:
            self.pool[hash].existed = True
            self.pool[hash].key = key
            self.pool[hash].val = value
            self.pool[hash].next_node = None
            return

    def get(self, key: int) -> int:
        """
        Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key
        """

        hash = key % self.capacity
        if self.pool[hash].existed:
            temp = self.pool[hash]
            while temp.next_node:
                if temp.key == key:
                    return temp.val
                temp = temp.next_node
            if temp.key == key:
                return temp.val
            return -1
        else:
            return -1

    def remove(self, key: int) -> None:
        """
        Removes the mapping of the specified value key if this map contains a mapping for the key
        """
        hash = key % self.capacity
        if not self.pool[hash].existed:
            return
        else:
            pre = None
            temp = self.pool[hash]
            while temp.next_node:
                if temp.key == key:
                    if not pre:
                        self.pool[hash] = temp.next_node
                    else:
                        pre.next_node = temp.next_node
                    return
                pre = temp
                temp = temp.next_node
            if temp.key == key:
                if not pre:
                    temp.existed = False
                else:
                    pre.next_node = None

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