IntersectionOfTwoLinkedLists

public class Solution {
    //如果两个链表的最后一个节点相同，则一定存在公共节点
    //长度长的链表先走几步，让两个链表对齐，之后开始一起遍历直到找到第一个公共节点
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if(headA==null||headB==null) {
            return null;
        }
        int lengthA = 1;
        int lengthB = 1;
        
        ListNode iterA = headA;
        while(iterA.next!=null) {
            iterA = iterA.next;
            lengthA++;
        }
        
        ListNode iterB = headB;
        while(iterB.next!=null) {
            iterB = iterB.next;
            lengthB++;
        }
        
        if(iterA!=iterB) {
            return null;
        }
        
        if(lengthA<lengthB) {
            int tmp = lengthA;
            lengthA = lengthB;
            lengthB = tmp;
        
            ListNode tmpListNode = headA;
            headA = headB;
            headB = tmpListNode;
        }
        
        
        int tmp = lengthA - lengthB;
        while(tmp>0) {
            headA = headA.next;
            tmp--;
        }
        
        while(headA!=headB) {
            headA = headA.next;
            headB = headB.next;
        }
        
        return headA;
    }
}