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.
Solution:
- use array to achive random access
- corner case collision -> linkedlist + while loop
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72class MyHashMap {
private static class Node {
final int key;
int value;
Node next;
public Node(int key, int value) {
this.key = key;
this.value = value;
}
}
final int SIZE = 10000;
Node[] array;
/** Initialize your data structure here. */
public MyHashMap() {
array = new Node[SIZE];
}
/** value will always be non-negative. */
public void put(int key, int value) {
int idx = hash(key);
Node head = array[idx];
Node node = head;
while (node != null) {
if (node.key == key) {
node.value = value;
return;
}
node = node.next;
}
Node newNode = new Node(key, value);
newNode.next = head;
array[idx] = newNode;
}
/** 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) {
int idx = hash(key);
Node node = array[idx];
while (node != null) {
if (node.key == key) {
return node.value;
}
node = node.next;
}
return -1;
}
/** Removes the mapping of the specified value key if this map contains a mapping for the key */
public void remove(int key) {
int idx = hash(key);
Node node = array[idx];
while (node != null) {
if (node.key == key) {
node.value = -1;
return;
}
node = node.next;
}
}
private int hash(int key) {
return Integer.hashCode(key) % SIZE;
}
}
/**
* 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);
*/