Merge pull request #200 from hdkn235/master

添加基于单链表实现LRU算法（java版）

Author: wangzheng0822

java/06_linkedlist/LRUBaseLinkedList.java

@@ -0,0 +1,176 @@
+package linked.singlelist;
+
+
+import java.util.Scanner;
+
+/**
+ * 基于单链表LRU算法（java）
+ *
+ * @author hoda
+ * @create 2018-12-17
+ */
+public class LRUBaseLinkedList<T> {
+
+    /**
+     * 默认链表容量
+     */
+    private final static Integer DEFAULT_CAPACITY = 10;
+
+    /**
+     * 头结点
+     */
+    private SNode<T> headNode;
+
+    /**
+     * 链表长度
+     */
+    private Integer length;
+
+    /**
+     * 链表容量
+     */
+    private Integer capacity;
+
+    public LRUBaseLinkedList() {
+        this.headNode = new SNode<>();
+        this.capacity = DEFAULT_CAPACITY;
+        this.length = 0;
+    }
+
+    public LRUBaseLinkedList(Integer capacity) {
+        this.headNode = new SNode<>();
+        this.capacity = capacity;
+        this.length = 0;
+    }
+
+    public void add(T data) {
+        SNode preNode = findPreNode(data);
+
+        // 链表中存在，删除原数据，再插入到链表的头部
+        if (preNode != null) {
+            deleteElemOptim(preNode);
+            intsertElemAtBegin(data);
+        } else {
+            if (length >= this.capacity) {
+                //删除尾结点
+                deleteElemAtEnd();
+            }
+            intsertElemAtBegin(data);
+        }
+    }
+
+    /**
+     * 删除preNode结点下一个元素
+     *
+     * @param preNode
+     */
+    private void deleteElemOptim(SNode preNode) {
+        SNode temp = preNode.getNext();
+        preNode.setNext(temp.getNext());
+        temp = null;
+        length--;
+    }
+
+    /**
+     * 链表头部插入节点
+     *
+     * @param data
+     */
+    private void intsertElemAtBegin(T data) {
+        SNode next = headNode.getNext();
+        headNode.setNext(new SNode(data, next));
+        length++;
+    }
+
+    /**
+     * 获取查找到元素的前一个结点
+     *
+     * @param data
+     * @return
+     */
+    private SNode findPreNode(T data) {
+        SNode node = headNode;
+        while (node.getNext() != null) {
+            if (data.equals(node.getNext().getElement())) {
+                return node;
+            }
+            node = node.getNext();
+        }
+        return null;
+    }
+
+    /**
+     * 删除尾结点
+     */
+    private void deleteElemAtEnd() {
+        SNode ptr = headNode;
+        // 空链表直接返回
+        if (ptr.getNext() == null) {
+            return;
+        }
+
+        // 倒数第二个结点
+        while (ptr.getNext().getNext() != null) {
+            ptr = ptr.getNext();
+        }
+
+        SNode tmp = ptr.getNext();
+        ptr.setNext(null);
+        tmp = null;
+        length--;
+    }
+
+    private void printAll() {
+        SNode node = headNode.getNext();
+        while (node != null) {
+            System.out.print(node.getElement() + ",");
+            node = node.getNext();
+        }
+        System.out.println();
+    }
+
+    public class SNode<T> {
+
+        private T element;
+
+        private SNode next;
+
+        public SNode(T element) {
+            this.element = element;
+        }
+
+        public SNode(T element, SNode next) {
+            this.element = element;
+            this.next = next;
+        }
+
+        public SNode() {
+            this.next = null;
+        }
+
+        public T getElement() {
+            return element;
+        }
+
+        public void setElement(T element) {
+            this.element = element;
+        }
+
+        public SNode getNext() {
+            return next;
+        }
+
+        public void setNext(SNode next) {
+            this.next = next;
+        }
+    }
+
+    public static void main(String[] args) {
+        LRUBaseLinkedList list = new LRUBaseLinkedList();
+        Scanner sc = new Scanner(System.in);
+        while (true) {
+            list.add(sc.nextInt());
+            list.printAll();
+        }
+    }
+}