706. Design HashMap

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.

搭建一个HashMap，通过一个表+链表实现，其中表大小设置为127，所有输入的key值映射到表头（key%127），链表用于解决冲突，链表元素为一对key，value，程序如下所示：

class MyHashMap {
    class Node{
        public int key;
        public int value;
        public Node(int k, int v){
            key = k;
            value = v;
        }
    }
    List> table = new ArrayList<>(127);

    /** Initialize your data structure here. */
    public MyHashMap() {
        for (int i = 0; i < 127; ++ i){
            table.add(new LinkedList());
        }
    }
    
    /** value will always be non-negative. */
    public void put(int key, int value) {
        List tmp = table.get(key%127);
        int len = tmp.size();
        for (int i = 0; i < len; ++ i){
            if (tmp.get(i).key == key){
                tmp.set(i, new Node(key, value));
                return;
            }
        }
        tmp.add(new Node(key, value));
    }
    
    /** Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key */
    public int get(int key) {
        List tmp = table.get(key%127);
        int len = tmp.size();
        for (int i = 0; i < len; ++ i){
            if (tmp.get(i).key == key){
                return tmp.get(i).value;
            }
        }
        return -1;
    }
    
    /** Removes the mapping of the specified value key if this map contains a mapping for the key */
    public void remove(int key) {
        List tmp = table.get(key%127);
        int len = tmp.size();
        for (int i = 0; i < len; ++ i){
            if (tmp.get(i).key == key){
                tmp.remove(i);
                return;
            }
        }
    }
}

/**
 * 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);
 */