映射（Map）是用于存取键值对的数据结构，一个键只能对应一个值且键不能重复。
基本方法接口：
/**
* className Map
* description TODO
*
* @author ln
* @version 1.0
* @date 2019/5/18 15:51
*/
public interface Map<K, V> {
void add(K key, V value);
V remove(K key);
boolean contains(K key);
V get(K key);
void set(K key, V newValue);
int getSize();
boolean isEmpty();
}
基于链表的映射实现
/**
* className LinkedListMap
* description TODO
*
* @author ln
* @version 1.0
* @date 2019/5/18 15:54
*/
public class LinkedListMap<K, V> implements Map<K, V> {
private class Node{
public K key;
public V value;
public Node next;
public Node(K key, V value, Node next){
this.key = key;
this.value = value;
this.next = next;
}
public Node(K key) {
this(key, null, null);
}
public Node() {
this(null, null, null);
}
@Override
public String toString() {
return key.toString() + " : " + value.toString();
}
}
private Node dummyHead;
private int size;
public LinkedListMap(){
dummyHead = new Node();
size = 0;
}
/**
* 辅助函数
* 根据key的值返回节点的引用
* @param key
* @return
*/
private Node getNode(K key){
Node cur = dummyHead.next;
while (cur != null){
if (cur.key.equals(key)){
return cur;
}
cur = cur.next;
}
return null;
}
@Override
public void add(K key, V value) {
Node node = getNode(key);
if (node == null){
dummyHead.next = new Node(key, value, dummyHead.next);
size++;
} else {
node.value = value;
}
}
@Override
public V remove(K key) {
Node prev = dummyHead;
while (prev.next != null){
if (prev.next.key.equals(key)){
break;
}
prev = prev.next;
}
if (prev.next != null){
Node delNode = prev.next;
prev.next = delNode.next;
delNode.next = null;
size--;
return delNode.value;
}
return null;
}
@Override
public boolean contains(K key) {
return getNode(key) != null;
}
@Override
public V get(K key) {
Node node = getNode(key);
return node == null ? null : node.value;
}
@Override
public void set(K key, V newValue) {
Node node = getNode(key);
if (node == null){
throw new IllegalArgumentException(key + "doesn't exist!");
}
node.value = newValue;
}
@Override
public int getSize() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
}
基于二分搜索树的映射实现
/**
* className BSTMap
* description TODO
*
* @author ln
* @version 1.0
* @date 2019/5/20 16:09
*/
public class BSTMap<K extends Comparable<K>, V> implements Map<K, V> {
private class Node{
public K key;
public V value;
public Node left, right;
public Node(K key, V value){
this.key = key;
this.value = value;
this.left = null;
this.right = null;
}
}
private Node root;
private int size;
public BSTMap(){
root = null;
size = 0;
}
/**
* 辅助函数
* 返回以node为根的二分搜索树中，key所在的节点
* @param node
* @param key
* @return
*/
private Node getNode(Node node, K key){
if (node == null){
return null;
}
if (key.compareTo(node.key) == 0){
return node;
} else if (key.compareTo(node.key) < 0){
return getNode(node.left, key);
} else {
return getNode(node.right, key);
}
}
@Override
public void add(K key, V value) {
root = add(root, key, value);
}
private Node add(Node node, K key, V value){
if (node == null){
size++;
return new Node(key, value);
}
if (key.compareTo(node.key) < 0){
node.left = add(node.left, key, value);
} else if (key.compareTo(node.key) > 0){
node.right = add(node.right, key, value);
} else {
node.value = value;
}
return node;
}
/**
* 返回以node为根的二分搜索树的最小值所在的节点
* @param node
* @return
*/
private Node minimum(Node node){
if (node.left == null){
return node;
}
return minimum(node.left);
}
/**
* 删除以node为根的二分搜索树的最小节点
* 返回删除节点后新的树的根
* @param node
* @return
*/
private Node removeMin(Node node){
if (node.left == null){
Node rightNode = node.right;
node.right = null;
size--;
return rightNode;
}
node.left = removeMin(node.left);
return node;
}
@Override
public V remove(K key) {
Node node = getNode(root, key);
if (node != null){
root = remove(root, key);
return node.value;
}
return null;
}
private Node remove(Node node, K key){
if (node == null){
return null;
}
if (key.compareTo(node.key) < 0){
node.left = remove(node.left, key);
return node;
} else if (key.compareTo(node.key) > 0){
node.right = remove(node.right, key);
return node;
} else {
/**
* 删除节点左子树为空
*/
if (node.left == null) {
Node rightNode = node.right;
node.right = null;
size--;
return rightNode;
}
/**
* 删除节点右子树为空
*/
if (node.right == null) {
Node leftNode = node.left;
node.left = null;
size--;
return leftNode;
}
/**
* 删除节点左右子树都不为空
* 思路：找到比待删除节点大的最小节点，即待删除节点右子树最小的节点
* 用这个节点代替删除节点的位置
*/
Node successor = minimum(node.right);
successor.right = removeMin(node.right);
successor.left = node.left;
node.right = node.left = null;
return successor;
}
}
@Override
public boolean contains(K key) {
return getNode(root, key) != null;
}
@Override
public V get(K key) {
Node node = getNode(root, key);
return node == null ? null : node.value;
}
@Override
public void set(K key, V newValue) {
Node node = getNode(root, key);
if (node == null){
throw new IllegalArgumentException(key + "doesn't exist!");
}
node.value = newValue;
}
@Override
public int getSize() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
}
有序映射和无序映射
有序映射中的键具有顺序性，基于搜索树实现。
无序映射中的键没有顺序性，基于哈希表实现。
Writtern by Autu.
2019.6.30
