Merge pull request #143 from quanxing/master

添加带头节点翻转和不带头节点翻转以及回文串的实现

java/06_linkedlist/SinglyLinkedList.java

@@ -8,160 +8,327 @@ package linkedlist;
  */
 public class SinglyLinkedList {
 
-  private Node head = null;
+    private Node head = null;
 
-  public Node findByValue(int value) {
-    Node p = head;
-    while (p != null && p.data != value) {
-      p = p.next;
+    public Node findByValue(int value) {
+        Node p = head;
+        while (p != null && p.data != value) {
+            p = p.next;
+        }
+
+        return p;
     }
 
-    return p;
-  }
+    public Node findByIndex(int index) {
+        Node p = head;
+        int pos = 0;
+        while (p != null && pos != index) {
+            p = p.next;
+            ++pos;
+        }
 
-  public Node findByIndex(int index) {
-    Node p = head;
-    int pos = 0;
-    while (p != null && pos != index) {
-      p = p.next;
-      ++pos;
+        return p;
     }
 
-    return p;
-  }
-
-  public void insertToHead(int value) {
-    Node newNode = new Node(value, null);
-    insertToHead(newNode);
-  }
-
-  public void insertToHead(Node newNode) {
-  if (head == null) {
-     head = newNode;
-    } else {
-      newNode.next = head;
-      head = newNode;
-    }
-  }
-
-  public void insertAfter(Node p, int value) {
-    Node newNode = new Node(value, null);
-    insertAfter(p, newNode);
-  }
-
-  public void insertAfter(Node p, Node newNode) {
-    if (p == null) return;
-
-    newNode.next = p.next;
-    p.next = newNode;
-  }
-
-  public void insertBefore(Node p, int value) {
-    Node newNode = new Node(value, null);
-    insertBefore(p, newNode);
-  }
-
-  public void insertBefore(Node p, Node newNode) {
-    if (p == null) return;
-    if (head == p) {
-      insertToHead(newNode);
-      return;
+    //无头结点
+    //表头部插入
+    //这种操作将于输入的顺序相反，逆序
+    public void insertToHead(int value) {
+        Node newNode = new Node(value, null);
+        insertToHead(newNode);
     }
 
-    Node q = head;
-    while (q != null && q.next != p) {
-      q = q.next;
+    public void insertToHead(Node newNode) {
+        if (head == null) {
+            head = newNode;
+        } else {
+            newNode.next = head;
+            head = newNode;
+        }
     }
 
-    if (q == null) {
-      return;
+    //顺序插入
+    //链表尾部插入
+    public void insertTail(int value){
+
+        Node newNode = new Node(value, null);
+        //空链表，可以插入新节点作为head，也可以不操作
+        if (head == null){
+            head = newNode;
+
+        }else{
+            Node q = head;
+            while(q.next != null){
+                q = q.next;
+            }
+            newNode.next = q.next;
+            q.next = newNode;
+        }
+    }
+    public void insertAfter(Node p, int value) {
+        Node newNode = new Node(value, null);
+        insertAfter(p, newNode);
     }
 
-    newNode.next = p;
-    q.next = newNode;
+    public void insertAfter(Node p, Node newNode) {
+        if (p == null) return;
 
-  }
-
-  public void deleteByNode(Node p) {
-    if (p == null || head == null) return;
-
-    if (p == head) {
-      head = head.next;
-      return;
+        newNode.next = p.next;
+        p.next = newNode;
     }
 
-    Node q = head;
-    while (q != null && q.next != p) {
-      q = q.next;
+    public void insertBefore(Node p, int value) {
+        Node newNode = new Node(value, null);
+        insertBefore(p, newNode);
     }
 
-    if (q == null) {
-      return;
+    public void insertBefore(Node p, Node newNode) {
+        if (p == null) return;
+        if (head == p) {
+            insertToHead(newNode);
+            return;
+        }
+
+        Node q = head;
+        while (q != null && q.next != p) {
+            q = q.next;
+        }
+
+        if (q == null) {
+            return;
+        }
+
+        newNode.next = p;
+        q.next = newNode;
+
     }
 
-    q.next = q.next.next;
-  }
+    public void deleteByNode(Node p) {
+        if (p == null || head == null) return;
 
-  public void deleteByValue(int value) {
-    if (head == null) return;
+        if (p == head) {
+            head = head.next;
+            return;
+        }
 
-    Node p = head;
-    Node q = null;
-    while (p != null && p.data != value) {
-      q = p;
-      p = p.next;
+        Node q = head;
+        while (q != null && q.next != p) {
+            q = q.next;
+        }
+
+        if (q == null) {
+            return;
+        }
+
+        q.next = q.next.next;
     }
 
-    if (p == null) return;
+    public void deleteByValue(int value) {
+        if (head == null) return;
 
-    if (q == null) {
-      head = head.next;
-    } else {
-      q.next = q.next.next;
+        Node p = head;
+        Node q = null;
+        while (p != null && p.data != value) {
+            q = p;
+            p = p.next;
+        }
+
+        if (p == null) return;
+
+        if (q == null) {
+            head = head.next;
+        } else {
+            q.next = q.next.next;
+        }
+
+        // 可重复删除指定value的代码
+        /*
+           if (head != null && head.data == value) {
+           head = head.next;
+           }
+
+           Node pNode = head;
+           while (pNode != null) {
+           if (pNode.next.data == data) {
+           pNode.next = pNode.next.next;
+           continue;
+           }
+           pNode = pNode.next;
+           }
+         */
     }
 
-    // 可重复删除指定value的代码
-    /*
-    if (head != null && head.data == value) {
-    	head = head.next;
+    public void printAll() {
+        Node p = head;
+        while (p != null) {
+            System.out.print(p.data + " ");
+            p = p.next;
+        }
+        System.out.println();
     }
 
-    Node pNode = head;
-    while (pNode != null) {
-    	if (pNode.next.data == data) {
-    		pNode.next = pNode.next.next;
-    		continue;
-    	}
-    	pNode = pNode.next;
+    //判断true or false
+    public boolean TFResult(Node left, Node right){
+        Node l = left;
+        Node r = right;
+
+        System.out.println("left_:"+l.data);
+        System.out.println("right_:"+r.data);
+        while(l != null && r != null){
+           if (l.data == r.data){
+               l = l.next;
+               r = r.next;
+               continue;
+           }else{
+               break;
+           }
+
+        }
+
+        System.out.println("什么结果");
+        if (l==null && r==null){
+           System.out.println("什么结果");
+           return true;
+        }else{
+           return false;
+        }
     }
-    */
-  }
+    //　判断是否为回文 
 
-  public void printAll() {
-    Node p = head;
-    while (p != null) {
-      System.out.print(p.data + " ");
-      p = p.next;
-    }
-    System.out.println();
-  }
+    public boolean palindrome(){
+       if (head == null){
+           return false;
+       }else{
+           System.out.println("开始执行找到中间节点");
+           Node p = head;
+           Node q = head;
+           if (p.next == null){
+               System.out.println("只有一个元素");
+               return true;
+           }
+           while( q.next != null && q.next.next != null){
+               p = p.next;
+               q = q.next.next;
 
-  public static Node createNode(int value) {
-    return new Node(value, null);
-  }
+           }
 
-  public static class Node {
-    private int data;
-    private Node next;
+           System.out.println("中间节点" + p.data);
+           System.out.println("开始执行奇数节点的回文判断");
+           Node leftLink = null;
+           Node rightLink = null;
+           if(q.next == null){
+               //　p 一定为整个链表的中点，且节点数目为奇数
+               leftLink = inverseLinkList(p);
+               System.out.println("左边第一个节点"+leftLink.data);
+               System.out.println("右边第一个节点"+p.next.data);
+               rightLink = p;
 
-    public Node(int data, Node next) {
-      this.data = data;
-      this.next = next;
+           }else{
+               //p q　均为中点
+               leftLink = inverseLinkList(p);
+               rightLink = q;
+           }
+           return TFResult(leftLink, rightLink);
+
+       }
     }
 
-    public int getData() {
-      return data;
+    //带结点的链表翻转
+    public Node inverseLinkList_head(Node p){
+        //　Head　为新建的一个头结点
+        Node Head = new Node(9999,null);
+        // p　为原来整个链表的头结点,现在Head指向　整个链表
+        Head.next = p;
+        /*
+        带头结点的链表翻转等价于
+        从第二个元素开始重新头插法建立链表
+        */
+        Node Cur = p.next;
+        p.next = null;
+        Node next = null;
+
+        while(Cur != null){
+            next = Cur.next;
+            Cur.next = Head.next;
+            Head.next = Cur;
+            System.out.println("first " + Head.data);
+
+            Cur = next;
+        }
+
+        //　返回左半部分的中点之前的那个节点
+        //　从此处开始同步像两边比较
+        return Head;
+
+    }
+
+    //无头结点的链表翻转
+    public Node inverseLinkList(Node p){
+
+        Node pre = null;
+        Node r = head;
+        System.out.println("z---" + r.data);
+        Node next= null;
+        while(r !=p){
+            next = r.next;
+
+            r.next = pre;
+            pre = r;
+            r = next;
+        }
+
+        r.next = pre;
+        //　返回左半部分的中点之前的那个节点
+        //　从此处开始同步像两边比较
+        return r;
+
+    }
+    
+    public static Node createNode(int value) {
+        return new Node(value, null);
+    }
+
+    public static class Node {
+        private int data;
+        private Node next;
+
+        public Node(int data, Node next) {
+            this.data = data;
+            this.next = next;
+        }
+
+        public int getData() {
+            return data;
+        }
+    }
+    public static void main(String[]args){
+
+        SinglyLinkedList link = new SinglyLinkedList(); 
+        System.out.println("hello");
+        //int data[] = {1};
+        //int data[] = {1,2,3,1};
+        int data[] = {1,2,4,5};
+        //int data[] = {1,2,2,1};
+        //int data[] = {1,2,5,2,1};
+
+        for(int i =0; i < data.length; i++){
+            //link.insertToHead(data[i]);
+            link.insertTail(data[i]);
+        }
+        link.printAll();
+        Node p = link.inverseLinkList_head(link.head);
+        while(p != null){
+            System.out.println("aa"+p.data);
+            p = p.next;
+        }
+
+        //System.out.println("打印原始:");
+        //link.printAll();
+        //if (link.palindrome()){
+        //    System.out.println("回文");
+        //}else{
+        //    System.out.println("不是回文");
+        //}
     }
-  }
 
 }