36两个链表的第一个公共结点

题目描述

1 public class Solution {
2     public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) {
3          int l1 = 0,l2 = 0,ldiff=0;
4         ListNode longp,shortp;
5
6         // 得到长度
7         for(ListNode p = pHead1;p!=null;p=p.next)
8             l1++;
9         for(ListNode p = pHead2;p!=null;p=p.next)
10             l2++;
11         if(l1>l2){
12             ldiff = l1-l2;
13             longp=pHead1;shortp = pHead2;
14         }
15            else{
16              ldiff = l2-l1;
17             longp=pHead2;shortp = pHead1;
18         }
19         //长链表先走
20         for(int i = 0;i<ldiff;i++){
21             longp = longp.next;
22         }
23         //2个链表同时遍历
24         while(longp!=null){
25             if(longp.val==shortp.val) return longp;
26             longp = longp.next;
27             shortp = shortp.next;
28
29         }
30         return null;
31     }
32 }