160. Intersection of Two Linked Lists

题目链接：https://leetcode.com/problems/intersection-of-two-linked-lists/

解题思路：

两个链表的公共节点，首先让长的链表先走length1-length2步，然后一起走

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        
        int lengthA= getlength(headA);
        int lengthB = getlength(headB);
    
        
        if(lengthA>lengthB)
        {
            for(int i=0;i<lengthA-lengthB;i++)
            {
                headA = headA.next;
            }
        }
        else
        {
            for(int i=0;i<lengthB-lengthA;i++)
            {
                headB = headB.next;
            }
        }
        
        while(headA!=headB)
        {
            headA=headA.next;
            headB = headB.next;
        }
        return headA;
    }
    public int getlength(ListNode node1)
    {
        int length=0;
        
        while(node1!=null)
        {
            length++;
            node1=node1.next;
        }
        return length;
    }
}