LeetCode: Design HashMap

Design HashMap

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• Tag: #oodesign

Design a HashMap without using any built-in hash table libraries.

To be specific, your design should include these functions:

• put(key, value) : Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value.
• get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
• remove(key) : Remove the mapping for the value key if this map contains the mapping for the key.

Example:

MyHashMap hashMap = new MyHashMap();
hashMap.put(1, 1);          
hashMap.put(2, 2);         
hashMap.get(1);            // returns 1
hashMap.get(3);            // returns -1 (not found)
hashMap.put(2, 1);          // update the existing value
hashMap.get(2);            // returns 1 
hashMap.remove(2);          // remove the mapping for 2
hashMap.get(2);            // returns -1 (not found) 

Note:

• All keys and values will be in the range of [0, 1000000].
• The number of operations will be in the range of [1, 10000].
• Please do not use the built-in HashMap library.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

• Solution:

// https://code.dennyzhang.com/design-hashmap
// Basic Ideas: array
// Complexity: Time O(1), Space O(1). 1,000,000 items
type MyHashMap struct {
    m []int
}


/** Initialize your data structure here. */
func Constructor() MyHashMap {
    res := MyHashMap{}
    res.m = make([]int, 1000001)
    for i, _ := range res.m {
        res.m[i] = -1
    }
    return res
}


/** value will always be non-negative. */
func (this *MyHashMap) Put(key int, value int)  {
    this.m[key] = value
}


/** Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key */
func (this *MyHashMap) Get(key int) int {
    return this.m[key]
}


/** Removes the mapping of the specified value key if this map contains a mapping for the key */
func (this *MyHashMap) Remove(key int)  {
    this.m[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);
 */