數(shù)據(jù)結(jié)構(gòu)（一）數(shù)組實(shí)現(xiàn)一個(gè)簡(jiǎn)單的ArrayList
數(shù)據(jù)結(jié)構(gòu)（二）鏈表實(shí)現(xiàn)LinkedList
數(shù)據(jù)結(jié)構(gòu)（三）用兩種方式簡(jiǎn)單實(shí)現(xiàn)棧
數(shù)據(jù)結(jié)構(gòu)（四）棧和隊(duì)列的簡(jiǎn)單應(yīng)用
數(shù)據(jù)結(jié)構(gòu)（五）用兩種方式簡(jiǎn)單實(shí)現(xiàn)隊(duì)列
數(shù)據(jù)結(jié)構(gòu)（六）二分搜索樹(Binary Search Tree)（上）
數(shù)據(jù)結(jié)構(gòu)（六）二分搜索樹(Binary Search Tree)（下）
數(shù)據(jù)結(jié)構(gòu)（七）兩種方式實(shí)現(xiàn)set
數(shù)據(jù)結(jié)構(gòu)（八）兩種方式實(shí)現(xiàn)map
數(shù)據(jù)結(jié)構(gòu)（九）set解決LeetCode349號(hào)問題
今天我們來實(shí)現(xiàn)一下map评雌，總共有兩種方式酝静，第一種是二分搜索樹實(shí)現(xiàn)map首妖，第二種方式鏈表實(shí)現(xiàn)map。
話不多說直接上源碼。
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;
}
@Override
public int getSize(){
return size;
}
@Override
public boolean isEmpty(){
return size == 0;
}
// 向二分搜索樹中添加新的元素(key, value)
@Override
public void add(K key, V value){
root = add(root, key, value);
}
// 向以node為根的二分搜索樹中插入元素(key, value)，遞歸算法
// 返回插入新節(jié)點(diǎn)后二分搜索樹的根
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 // key.compareTo(node.key) == 0
node.value = value;
return node;
}
// 返回以node為根節(jié)點(diǎn)的二分搜索樹中，key所在的節(jié)點(diǎn)
private Node getNode(Node node, K key){
if(node == null)
return null;
if(key.equals(node.key))
return node;
else if(key.compareTo(node.key) < 0)
return getNode(node.left, key);
else // if(key.compareTo(node.key) > 0)
return getNode(node.right, key);
}
@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;
}
// 返回以node為根的二分搜索樹的最小值所在的節(jié)點(diǎn)
private Node minimum(Node node){
if(node.left == null)
return node;
return minimum(node.left);
}
// 刪除掉以node為根的二分搜索樹中的最小節(jié)點(diǎn)
// 返回刪除節(jié)點(diǎn)后新的二分搜索樹的根
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;
}
// 從二分搜索樹中刪除鍵為key的節(jié)點(diǎn)
@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{ // key.compareTo(node.key) == 0
// 待刪除節(jié)點(diǎn)左子樹為空的情況
if(node.left == null){
Node rightNode = node.right;
node.right = null;
size --;
return rightNode;
}
// 待刪除節(jié)點(diǎn)右子樹為空的情況
if(node.right == null){
Node leftNode = node.left;
node.left = null;
size --;
return leftNode;
}
// 待刪除節(jié)點(diǎn)左右子樹均不為空的情況
// 找到比待刪除節(jié)點(diǎn)大的最小節(jié)點(diǎn), 即待刪除節(jié)點(diǎn)右子樹的最小節(jié)點(diǎn)
// 用這個(gè)節(jié)點(diǎn)頂替待刪除節(jié)點(diǎn)的位置
Node successor = minimum(node.right);
successor.right = removeMin(node.right);
successor.left = node.left;
node.left = node.right = null;
return successor;
}
}
public static void main(String[] args){
System.out.println("Pride and Prejudice");
ArrayList<String> words = new ArrayList<>();
if(FileOperation.readFile("pride-and-prejudice.txt", words)) {
System.out.println("Total words: " + words.size());
BSTMap<String, Integer> map = new BSTMap<>();
for (String word : words) {
if (map.contains(word))
map.set(word, map.get(word) + 1);
else
map.add(word, 1);
}
System.out.println("Total different words: " + map.getSize());
System.out.println("Frequency of PRIDE: " + map.get("pride"));
System.out.println("Frequency of PREJUDICE: " + map.get("prejudice"));
}
System.out.println();
}
}
- add方法
這個(gè)node與之前鏈表的node有點(diǎn)不太一樣，這里多了一個(gè)value株扛，指針變成了left和right尤筐。這個(gè)add方法我們用遞歸的方式實(shí)現(xiàn)的，當(dāng)這個(gè)節(jié)點(diǎn)是空的時(shí)候我們就創(chuàng)建一個(gè)節(jié)點(diǎn)洞就，如果這個(gè)節(jié)點(diǎn)不是空的：先比較可以與當(dāng)前節(jié)點(diǎn)的元素盆繁，如果比當(dāng)前節(jié)點(diǎn)的元素小則去這個(gè)節(jié)點(diǎn)的左子樹去處理；如果比當(dāng)前節(jié)點(diǎn)的元素大旬蟋，那么就去這個(gè)節(jié)點(diǎn)的右子樹去遍歷油昂，如果相等那么就把值賦給這個(gè)節(jié)點(diǎn)。 - getNode
獲取方法倾贰，獲取值為key的節(jié)點(diǎn)元素的value冕碟。這里也是遞歸的方式實(shí)現(xiàn)的，首先如果這個(gè)節(jié)點(diǎn)是空的匆浙，就返回null安寺，然后比較這個(gè)節(jié)點(diǎn)的值與傳入的key，如果相等首尼，就返回當(dāng)前的節(jié)點(diǎn)挑庶，如果比這個(gè)節(jié)點(diǎn)小那么就去這個(gè)節(jié)點(diǎn)的左子樹去遍歷，如果比這個(gè)節(jié)點(diǎn)的值大就去這個(gè)節(jié)點(diǎn)的右子樹去遍歷软能。
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, V value){
this(key, value, 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;
}
@Override
public int getSize(){
return size;
}
@Override
public boolean isEmpty(){
return 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 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 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 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 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;
}
public static void main(String[] args){
System.out.println("Pride and Prejudice");
ArrayList<String> words = new ArrayList<>();
if(FileOperation.readFile("pride-and-prejudice.txt", words)) {
System.out.println("Total words: " + words.size());
LinkedListMap<String, Integer> map = new LinkedListMap<>();
for (String word : words) {
if (map.contains(word))
map.set(word, map.get(word) + 1);
else
map.add(word, 1);
}
System.out.println("Total different words: " + map.getSize());
System.out.println("Frequency of PRIDE: " + map.get("pride"));
System.out.println("Frequency of PREJUDICE: " + map.get("prejudice"));
}
System.out.println();
}
}
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