链表相关面试算法题 java实现

package link;


import java.util.Stack;


public class LinkList {
private Node head;
private Node current;
class Node{
int data;
Node next;
public Node(int data){
this.data = data;
}
}

//链表的添加
public void add(int data){
if(head == null){
head = new Node(data);
current = head;
}else{
current.next = new Node(data);
current = current.next;
}
}

//链表的打印
public void print(Node node){
if(node == null){
return;
}
current = node;
while(current != null){
System.out.println(current.data);
current = current.next;
}
}

public static void main(String[] args){
LinkList list = new LinkList();
for(int i=0;i<10;i++){
list.add(i);
}
// list.print(list.head);
// System.out.println("length = "+list.getLength(list.head));
// System.out.println("mid = "+list.findMidNode(list.head).data);

LinkList list1 = new LinkList();
        LinkList list2 = new LinkList();
        //向LinkList中添加数据
        for (int i = 0; i < 4; i++) {
            list1.add(i);
        }


        for (int i = 0; i < 8; i++) {
            list2.add(i);
        }


        LinkList list3 = new LinkList();
        list3.head = list3.mergeLinkList(list1.head, list2.head); //将list1和list2合并，存放到list3中


        list3.print(list3.head);// 从head节点开始遍历输出
}

//获取链表的长度
private int getLength(Node head){
if(head == null){
return 0;
}
int length = 0;
Node current = head;
while(current != null){
length ++;
current = current.next;
}
return length;
}

public int findLastNode(Node head,int index){
if(head == null){
return -1;
}
int size = 0;
current = head;
while(current != null){
size++;
current = current.next;
}
current = head;
for(int i=0;i<size - index ;i++){
current = current.next;
}
return current.data;
}

private Node findLastNode2(Node head , int k){
if(k == 0 || head == null){
return null;
}
Node q = head;
Node h = head;
for(int i=0;i<k-1;i++){
h = h.next;
if(h == null){
return null;
}
}
while(h.next != null){
q = q.next;
h = h.next;
}
return q;
}

//查找中间节点
private Node findMidNode(Node head){
if(head == null){
return null;
}
Node q = head;
Node h = head;
while(h != null && h.next != null){
q = q.next;
h = h.next.next;
}
return q;
}


private Node mergeLinkList(Node head1,Node head2){
if(head1 == null && head2 == null){
return null;
}
if(head1 == null){
return head2;
}
if(head2 == null){
return head1;
}
Node head;
Node current;
if(head1.data < head2.data){
head = head1;
current = head1;
head1 = head1.next;
}else{
head = head2;
current = head2;
head2 = head2.next;
}

while(head1 != null && head2 != null){
if(head1.data < head2.data){
current.next = head1;
current = current.next;
head1 = head1.next;
}else{
current.next = head2;
current = current.next;
head2 = head2.next;
}
}

if(head1 != null){
current.next = head1;
}

if(head2 != null){
current.next = head2;
}
return head;
}

//链表反转
private Node reverseList(Node head){
if(head == null || head.next == null){
return head;
}

Node current = head;
Node next = null;
Node reverseHead = null;

while(current != null){
next = current.next;

current.next = reverseHead;
reverseHead = current;

current = next;
}
return reverseHead;
}

//从尾到头打印单链表
private void reversePrint(Node head){
if(head == null){
return;
}
Stack<Node> stack = new Stack<Node>();
Node current = head;
while(current != null){
stack.push(current);
current = current.next;
}
while(stack.size() > 0){
System.out.println(stack.pop().data);
}
}

private void reversePrint2(Node head){
if(head == null){
return;
}
reversePrint2(head.next);
System.out.println(head.data);
}

//判断链表是否有环
private boolean hasCycle(Node head){
if(head == null){
return false;
}
Node q = head;
Node h = head;
while(h != null){
q = q.next;
h = h.next.next;

if(q == h){
return true;
}
}
return false;
}


//链表有环时 相遇的节点
private Node hasCycle2(Node head){
if(head == null){
return null;
}
Node q = head;
Node h = head;
while(q != null){
q = q.next.next;
h = h.next;
if(q == h){
return q;
}
}
return null;
}

private int getCycleLenngth(Node node){
if(head == null){
return 0;
}
Node current = node;
int length = 0;
while(current != null){
current = current.next;
length++;
if(current == node){
return length;
}
}
return length;
}

//有环的链表 起始位置 
private Node getCycleStart(Node head,int cycleLength){
if(head == null){
return null;
}
Node q = head;
Node h = head;
for(int i = 0; i<cycleLength;i++){
h = h.next;
}
while(q != null &&h != null){
q = q.next;
h = h.next;
if(q == h){
return q;
}
}
return null;
}

//两个单链表相交的第一个节点
private Node getFirstCommonNode(Node head1, Node head2){
if(head1 == null || head2 == null){
return null;
}
int length1 = getLength(head1);
int length2 = getLength(head2);

int lengthDif = 0;

Node longHead;
Node shortHead;

if(length1 > length2){
longHead = head1;
shortHead = head2;
lengthDif = length1 - length2;
} else {
longHead = head2;
shortHead = head1;
lengthDif = length2 - length1;
}

//将较长的那个链表的指针向前走length个距离
for(int i=0;i<lengthDif;i++){
longHead = longHead.next;
}

while(longHead != null && shortHead != null){
if(longHead == shortHead){
return longHead;
}
longHead = longHead.next;
shortHead = shortHead.next;
}

return null;
}










































}