160. 相交链表

 1 ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
 2     if (headA == nullptr || headB == nullptr)
 3         return nullptr;
 4     ListNode* tempa = headA;
 5     ListNode* tempb = headB;
 6     ListNode* res = nullptr;
 7     int count1 = 0;
 8     int count2 = 0;
 9 
10     while (count1 < 2 && count2 < 2)
11     {
12         if (count1 == 1 && count2 == 1 && tempa == tempb)
13         {
14             res = tempa;
15             break;
16         }
17         tempa = tempa->next;
18         if (tempa == nullptr)
19         {
20             tempa = headB;
21             count1++;
22         }
23         tempb = tempb->next;
24         if (tempb == nullptr)
25         {
26             tempb = headA;
27             count2++;
28         }
29     }
30     return res;
31 }

 1 ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
 2     if (headA == nullptr || headB == nullptr)
 3         return nullptr;
 4     ListNode* tempa = headA;
 5     while (tempa->next != nullptr)
 6     {
 7         tempa = tempa->next;
 8     }
 9     tempa->next = headA;
10 
11     ListNode* fast = headB;
12     ListNode* slow = headB;
13     while (fast != nullptr &&fast->next != nullptr)
14     {
15         fast = fast->next->next;
16         slow = slow->next;
17         if (fast == slow)
18         {
19             break;
20         }
21     }
22     if (fast == nullptr || fast->next==nullptr)
23     {
24         tempa->next = nullptr;
25         return nullptr;
26     }
27         
28     slow = headB;
29     while (slow != fast)
30     {
31         slow = slow->next;
32         fast = fast->next;
33     }
34     tempa->next = nullptr;
35     return slow;
36 }