两个有公共结点而部分重叠的单链表，拓扑形状看起来像Y  而非X

LinkList Search_1st_Common(LinkList L1 , LinkList L2){  int len1 = length(L1),  len2 = length(2);  LinkLsit longlist, shortlist;  int dist;  if(len1 > len2){    longlist = L1>next;  shortlist = L2->next;    dist = len1 - len2;  else{    longlist = L2>next;  shortlist = L1->next;    dist = len2 - len1;   while(dist--)    longlist = longlist->next;    while(longlist !=NULL){    if(longlist == shortlist)        return longlist;    else{        longlist = longlist->next;        shortlist = shortlist->next;    }  }return NULL;}        }