我要好offer之 链表大总结

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/

ListNode* DeleteNode(ListNode* pHead, ListNode* deletedNode) {
assert(pHead != NULL && deletedNode != NULL);
ListNode newHead(-1);
newHead.next = pHead;
if (pHead == deletedNode) {
newHead->next = pHead->next;
delete deletedNode;
deketedNode = NULL;
return newHead.next;
} else {
if (deleteNode->next == NULL) {
ListNode* cur = pHead;
while (cur->next != deleteNode) {
cur = cur->next;
}
cur->next = NULL;
delete deletedNode;
deletedNode = NULL;
return newHead.next;
} else {
ListNode* nextNode = deletedNode->next;
deletedNode->val = nextNode->val;
deletedNode->next = nextNode->next;
delete nextNode;
nextNode = NULL;
return newHead.next;
}
}
}

ListNode* ReverseList(ListNode* pHead) {
if (pHead == NULL || pHead->next == NULL) {
return pHead;
}
ListNode* tail = pHead;
ListNode* cur = pHead->next;
while (cur != NULL) {
ListNode* nextNode = cur->next;
cur->next = pHead;
pHead = cur;
cur = nextNode;
}
tail->next = NULL;
return pHead;
}

ListNode* KthNode(ListNode* pHead, int k) {
assert(pHead != NULL && k > 0);
ListNode* first = pHead;
ListNode* second = pHead;
while (first != NULL && k > 0) {
first = first->next;
--k;
}
if (first == NULL) {
if (k == 0) {
return pHead;
} else {
return NULL;
}
}
while (first != NULL) {
first = first->next;
second = second->next;
}
return second;
}

class Solution {
public:
ListNode *sortList(ListNode *head) {
if (head == NULL || head->next == NULL) {
return head;
}

ListNode* slow = head;
ListNode* fast = head;
//快慢指针找链表中间结点
while (fast != NULL && fast->next != NULL && fast->next->next != NULL) {
slow = slow->next;
fast = fast->next->next;
}
ListNode* list1 = head;
ListNode* list2 = slow->next;
slow->next = NULL;
ListNode* sortList1 = sortList(list1);
ListNode* sortList2 = sortList(list2);
ListNode* res = mergeSortList(sortList1, sortList2);
return res;
}

ListNode* mergeSortList(ListNode* list1, ListNode* list2) {
if (list1 == NULL) return list2;
if (list2 == NULL) return list1;
ListNode newHead(-1);
ListNode* cur = &newHead;
ListNode* node1 = list1;
ListNode* node2 = list2;
while (node1 != NULL && node2 != NULL) {
if (node1->val <= node2->val) {
cur->next = node1;
node1 = node1->next;
cur = cur->next;
} else {
cur->next = node2;
node2 = node2->next;
cur = cur->next;
}
}
while (node1 != NULL) {
cur->next = node1;
node1 = node1->next;
cur = cur->next;
}
while (node2 != NULL) {
cur->next = node2;
node2 = node2->next;
cur = cur->next;
}
return newHead.next;
}
};