JZ52 两个链表的第一个公共结点

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) {
        
        if (pHead1 == null || pHead2 == null)
            return null;
        
       
        
        ListNode p1=pHead1;
        ListNode p2=pHead2;
        int len1=getlen(pHead1);
        int len2=getlen(pHead2);
        
        if(len1>len2){
            int len=len1-len2;
            while(len>0){
                p1=p1.next;
                len--;
            }
        }
        
        if(len1<len2){
            int len=len2-len1;
            while(len>0){
                p2=p2.next;
                len--;
            }
        }
        
        while(p1!=p2){
            p1=p1.next;
            p2=p2.next;
        }
        
        return p1;
        
 
    }
    
    
     public static int getlen(ListNode l){
            int len=0;
            ListNode temp=l;
            while(temp!=null){
                len++;
                temp=temp.next;
            }
            return len;
        }
}