/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
 typedef struct ListNode ListNode;
struct ListNode *getIntersectionNode(struct ListNode *headA, struct ListNode *headB) {
    //先求出两个链表的长度
    ListNode*curA=headA;
    int la=0;
    while(curA){
        ++la;
        curA=curA->next;
    }
    ListNode*curB=headB;
    int lb=0;
    while(curB){
        ++lb;
        curB=curB->next;
    }
    //短的按兵不动，长的运动直至与短的相等长度
    ListNode*longList=headA;
    ListNode*shortList=headB;
    if(lb>la){
        longList=headB;
        shortList=headA;
    }

    int gap=abs(la-lb);
    while(gap--){//长的先走
        longList=longList->next;
    }
    while(longList){
        if(longList==shortList)
            return longList;
        
        longList=longList->next;
        shortList=shortList->next;
    }
    return NULL;

}