「架构师训练营第 1 期」第八周作业

/*
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;
        int len1=0,len2=0; // 计算链表长度
        ListNode p1=pHead1,p2=pHead2;
        while(p1!=null){
            p1=p1.next;
            len1++;
        }
        while(p2!=null){
            p2=p2.next;
            len2++;
        }
        p1=pHead1;p2=pHead2;
      	//移动更长的链表
        if(len1>len2){
            p1 = moveSome(pHead1,len1-len2);
        }else{
            p2 = moveSome(pHead2,len2-len1);
        }
       //找到相交节点
        while(p1!=p2&&p1!=null&&p2!=null){
            p1=p1.next;
            p2=p2.next;
        }
         
        return p1;
    }
     
    public ListNode moveSome(ListNode p,int step){
        for(int i=0;i<step;i++){
            p=p.next;
        }
        return p;
    }
}