876. 链表的中间结点

代码

/*** Definition for singly-linked list.* struct ListNode {*     int val;*     ListNode *next;*     ListNode() : val(0), next(nullptr) {}*     ListNode(int x) : val(x), next(nullptr) {}*     ListNode(int x, ListNode *next) : val(x), next(next) {}* };*/
class Solution {
public:ListNode* middleNode(ListNode* head) {ListNode * slow = head, * fast = head;while(fast && fast -> next){slow = slow->next;fast = fast->next->next;}//找中间节点return slow;}
};

876. 链表的中间结点

代码

141. 环形链表

代码

/*** Definition for singly-linked list.* struct ListNode {*     int val;*     ListNode *next;*     ListNode(int x) : val(x), next(NULL) {}* };*/
class Solution {
public:bool hasCycle(ListNode *head) {ListNode * slow = head, * fast = head;while(fast && fast -> next){slow = slow->next;fast = fast -> next -> next;if(slow == fast) return true;}return false;}
};

142. 环形链表 II

代码

/*** Definition for singly-linked list.* struct ListNode {*     int val;*     ListNode *next;*     ListNode(int x) : val(x), next(NULL) {}* };*/
class Solution {
public:ListNode *detectCycle(ListNode *head) {ListNode * slow = head, *fast = head;while(fast && fast -> next){slow = slow -> next;fast = fast -> next -> next;if(slow == fast){while(head != slow){head = head->next;slow = slow -> next;}return slow;}}return NULL;}
};

LCR 026. 重排链表

代码

/*** Definition for singly-linked list.* struct ListNode {*     int val;*     ListNode *next;*     ListNode() : val(0), next(nullptr) {}*     ListNode(int x) : val(x), next(nullptr) {}*     ListNode(int x, ListNode *next) : val(x), next(next) {}* };*/
class Solution {
public:void reorderList(ListNode* head) {ListNode * slow = head, * fast = head;while(fast && fast -> next){slow = slow->next;fast = fast->next->next;}//找中间节点ListNode * prev = nullptr, * cur = slow;while(cur){ListNode * tp = cur -> next;cur -> next = prev;prev = cur;cur = tp;}//反转后半段链表ListNode * head2 = prev, *head1 = head;while(head2 -> next){ListNode * tp1 = head1->next, * tp2 = head2 -> next;head2->next = head1->next;head1->next = head2;head1 = tp1;head2 = tp2;}//令交错指向，最终head2的下一个为空结束}
};