数据结构之链表

package com.dby.link;/** * Created by suzunshou on 2016/4/11. * 链表的元素不能随机访问 * 元素前面和后面不会出现多个元素相连的情况 * 元素相互依赖，串联而成 * 链表只有一个表头 */public class LinkedList {    //结点类    private class Node {        //数据        private Object data;        //下一个结点的地址        private Node next = null;        public Node(Object data) {            this.data = data;        }    }    private Node first = null;    private Node last = null;    private int size;    //在首部插入结点    public void insertFirst(Object data) {        //创建一个新结点        Node newNode = new Node(data);        //结点指向原来的first结点        newNode.next = first;        //将结点赋值给first结点        first = newNode;        Node p = first;        Node q = null;        //遍历查找最后一个结点        while (p != null) {            q = p;            p = p.next;        }        //将结点放到尾结点        last = q;        size++;    }    //链表尾部插入结点    public void insertLast(Object data) {        //新结点        Node newNode = new Node(data);        //空链表的话，新结点放first        if (first == null) {            first = newNode;        } else {            Node p = first;            Node q = null;            //遍历查找最后一个结点            while (p != null) {                q = p;                p = p.next;            }            //将结点放到尾结点            q.next = newNode;            last = newNode;        }        size++;    }    //插入结点到某个位置    public void insert(Object data, int index) {        //新结点        Node newNode = new Node(data);        //空链表        if (first == null) {            first = newNode;            return;        }        //只有一个结点        if (index - 1 == 0) {            newNode.next = first;            first = newNode;            return;        }        //普通情况        Node curr = first;        int count = 0;        //遍历找到索引处的结点        while (curr.next != null && count < index - 2) {            curr = curr.next;            count++;        }        //插入结点，把前一个结点和后一个结点断开，两端接上新结点        if (count == index - 2) {            newNode.next = curr.next;            curr.next = newNode;        }    }    //查找所有结点    public void findAll() {        //空结点        if (first == null)            return;        //遍历结点        Node cur = first;        while (cur != null) {            System.out.print(cur.data + "->");            cur = cur.next;        }        System.out.println("\n");    }    //反转链表    public void reverse() {        //空链表        if (first == null) {            return;        }        Node next_node, curr_node;        //第二个结点        curr_node = first.next;        //断开第一第二个结点        first.next = null;        //反转相当于每次都findOne+insertFirst        while (curr_node != null) {            //第三个结点            next_node = curr_node.next;            //把第一个结点接到第二个结点的另一端            curr_node.next = first;            //把第二个结点变成新的第一个结点            first = curr_node;            //移动到下一个结点            curr_node = next_node;        }    }    //删除首结点    public void deleteFirst() {        //空结点        if (first == null)            return;        //指针移向first结点指向的结点的下一个结点        first = first.next;        size--;    }    //删除尾结点    public void deleteLast() {        //空链表        if (first == null)            return;        //只有一个结点        if (first.next == null) {            first = null;            size--;        } else {            //多个结点            Node p = first;            Node q = null;            //遍历结点，找出倒数第2个结点            while (p.next != null) {                q = p;                p = p.next;            }            //删除最后一个结点            q.next = null;            size--;        }    }    //根据数据查找结点    public Node findOne(Object data) {        //空链表        if (first == null)            return null;        //令当前结点为first结点        Node cur = first;        //遍历结点        while (cur != null) {            //查找到了，返回            if (cur.data.equals(data)) {                return cur;            } else {                //否则，继续查找下一个结点                cur = cur.next;            }        }        return null;    }    //根据索引找出结点    public Node findByIndex(int index) {        if (index - 1 > size) {        } else {            Node curr = first;            for (int i = 1; i < index; i++) {                curr = curr.next;            }            return curr;        }        return null;    }    //是否为空    public boolean isEmpty() {        return (size == 0);    }    //删除某一个结点    public void remove(Object data) {        //空链表        if (first == null) {            return;        }        //单结点链表        if (first.data.equals(data)) {            first = first.next;            size--;        } else {            //前一个结点            Node prev = first;            //中间结点            Node cur = first.next;            while (cur != null) {                if (cur.data.equals(data)) {                    //后一个结点接到前一个结点，顶替中间结点                    prev.next = cur.next;                    size--;                }                //否则，前一个结点移动到下一个结点                prev = cur;                //中间结点移动到下一个结点                cur = cur.next;            }        }    }    //根据索引删除结点    public void removeByIndex(int index) {        //空链表        if (first == null) {            return;        }        //单结点        Node curr = first;        int count = 0;        if (index - 1 == 0) {            first = first.next;            return;        }        //普通情况，找到结点        while (curr.next != null && count < index - 2) {            curr = curr.next;            count++;        }        //删除结点        if (count == index - 2 && curr.next != null) {            Node delete_node = curr.next;            curr.next = delete_node.next;            delete_node = null;        }        size--;    }    public static void main(String[] args) {        LinkedList ll = new LinkedList();        for (int i = 1; i < 8; i++) {            ll.insertLast(i);        }        ll.removeByIndex(2);        ll.removeByIndex(4);        ll.findAll();        System.out.println(ll.findByIndex((ll.size + 1) / 2).data);        ll.insert(2,2);        ll.insertFirst(0);        System.out.println(ll.findOne(2).data);        ll.findAll();    }}