The first common node of the two linked lists of the offer (44)

Title Description

Enter two linked lists to find their first common node.

Thinking analysis: Will one of the linked list node, deposit into the HashMap, will use ContainsKey () to determine whether there is a common node

Code Listing 1:

<span style= "color: #6600cc;" >import java.util.*;p Ublic class Solution {public    ListNode findfirstcommonnode (ListNode pHead1, ListNode pHead2 ) {        ListNode p=phead1;        ListNode q=phead2;        Hashmap<listnode,integer> map=new hashmap<listnode,integer> ();        while (p!=null) {            map.put (p,null);            P=p.next;        }        while (q!=null) {            if (Map.containskey (q)) {                return q;            } else{                q=q.next;            }        }        return null;}    } </span>

Code Listing 2:

<span style= "color: #cc33cc;" >public class Solution {public ListNode Findfirstcommonnode (ListNode pHead1, ListNode pHead2) {ListNode cu Rrent1 = phead1;//List 1 ListNode current2 = phead2;//List 2 if (PHead1 = = NULL | | pHead2 = NULL) RE        Turn null;        int length1 = GetLength (current1);        int length2 = GetLength (Current2);             The length difference of the two even tables//if the length of the list 1 is greater than the length of the list 2 if (length1 >= length2) {int len = length1-length2;                Go through the list 1, the length of the traverse is the length difference between the two linked lists while (len > 0) {current1 = Current1.next;            len--;            }}//If the length of the list 2 is greater than the length of the linked list 1 else if (Length1 < length2) {int len = length2-length1;                Go through the list 1, the length of the traverse is the length difference between the two linked lists while (len > 0) {current2 = Current2.next;            len--; }}//begins to go hand in hand until the first common node is found while (Current1!=current2) {current1=curRent1.next;        Current2=current2.next;     } return current1;         }//To specify the length of the linked list public static int getlength (ListNode phead) {int length = 0;        ListNode current = Phead;            while (current! = null) {length++;        current = Current.next;     } return length; }}</span>

The first common node of the two linked lists of the offer (44)