双指针-链表-面试题52. 两个链表的第一个公共节点

解题思路：

设交集链表长c,链表1除交集的长度为a，链表2除交集的长度为b，有

• a + c + b = b + c + a

• 若无交集，则a + b = b + a

 

/**
 * 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) {
        ListNode h1=headA,h2=headB;
        while(h1!=h2){
            h1=h1==null?headB:h1.next;
            h2=h2==null?headA:h2.next;
        }
        return h1;  
    }
}