Write a program to find the node at which the intersection of two singly linked lists begins.
For example, the following two linked lists:
A: a1 → a2
↘
c1 → c2 → c3
↗
B: b1 → b2 → b3
begin to intersect at node c1.
1 /** 2 * Definition for singly-linked list. 3 * struct ListNode { 4 * int val; 5 * ListNode *next; 6 * ListNode(int x) : val(x), next(NULL) {} 7 * }; 8 */ 9 class Solution { 10 public: 11 ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) { 12 if(!headA){ 13 return NULL; 14 }else if(!headB){ 15 return NULL; 16 } 17 ListNode* ListLong = headA; 18 ListNode* ListShort = headB; 19 20 int length1 = GetListLength(headA); 21 int length2 = GetListLength(headB); 22 int diffLength = length1 - length2; 23 24 if(length2 > length1){ 25 ListLong = headB; 26 ListShort = headA; 27 diffLength = length2 - length1; 28 } 29 30 for(int i = 0 ; i < diffLength; i++){ 31 ListLong = ListLong->next; 32 } 33 34 while((ListLong != NULL) && (ListShort != NULL) && (ListLong != ListShort)){ 35 ListLong = ListLong->next; 36 ListShort = ListShort->next; 37 } 38 39 ListNode* CommonNode = ListLong; 40 return CommonNode; 41 42 } 43 unsigned int GetListLength(ListNode* pHead){ 44 unsigned int length = 0; 45 ListNode* pNode = pHead; 46 while(pNode != NULL){ 47 ++length; 48 pNode = pNode->next; 49 } 50 return length; 51 } 52 };