LeetCode 面试题02.07. 链表相交

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
        ListNode *hA=headA;
        ListNode *hB=headB;
        int l1=0,l2=0;
        while(hA){
            l1++;
            hA=hA->next;
        }
        while(hB){
            l2++;
            hB=hB->next;
        }
        int sub;
        if(l1>l2){
            sub=l1-l2;
            while(sub){
                headA=headA->next;
                sub--;
            }
        }
        else{
            sub=l2-l1;
            while(sub){
                headB=headB->next;
                sub--;
            }
        }
        while(headA){
            if(headA==headB){
                return headA;
            }
            headA=headA->next;
          
            headB=headB->next;
        }
        return NULL;
    }
};