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1 基于链表的映射实现
Map.java
package setAndmap;
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();
}
LinkedListMap.java
package setAndmap;
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;
}
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 + " not exists");
}
node.value = newValue;
}
@Override
public int getSize() {
return 0;
}
@Override
public boolean isEmpty() {
return false;
}
}
2 基于二分搜索树的映射的实现
BSTMap.java
package setAndmap;
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;
left = null;
right = null;
}
}
private Node root;
private int size;
public BSTMap() {
root = null;
size = 0;
}
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);
}
//向以 node 为根的二分搜索树种插入元素(key,value)
// 返回插入新节点后二分搜索树的根
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;
}、
@Override
public V remove(K key) {
Node node = getNode(root, key);
if (node != null) {
root = remove(root, key);
return node.value;
}
return null;
}
//返回以 node 为根的二分搜索树的最小值所在的节点
private Node minimum(Node node) {
if (node.left == null) {
return node;
}
return minimum(node.left);
}
// 删除以 node 为根的二分搜索树中的最小节点
// 返回删除节点后新的二分搜索树的根
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;
}
// 删除以node 为根的二分搜索树中键为 key 的节点，递归算法
// 返回删除节点后新的二分搜索树的根
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 { // key.compareTo(node.key) == 0
// 待删除节点左子树为空
if (node.left == null) {
Node rightNode = node.right;
node.right = null;
size--;
return rightNode;
}
if (node.right == null) {
Node leftNode = node.left;
node.left = null;
size--;
return leftNode;
}
/*
* 待删除节点左右子树均不为空
*
* 找到比待删除节点大的最小节点，即待删除节点右子树的最小节点
*
* 用这个节点顶替待删除的节点的位置
*
* */
Node successor = minimum(node.right);
successor.right = removeMin(node.right);
successor.left = node.left;
node.left = node.right = 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 + " not exist");
}
node.value = newValue;
}
@Override
public int getSize() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
}
3 有序和无序映射
- 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