leetcode 83和84 Remove Duplicates from Sorted List 和leetcode 1836

目录

83. Remove Duplicates from Sorted List

82. Remove Duplicates from Sorted List II

1836. Remove Duplicates From an Unsorted Linked List

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删除链表中的结点合集

83. Remove Duplicates from Sorted List

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* deleteDuplicates(ListNode* head) {if(head == nullptr)return head;ListNode* pre = head;ListNode* cur = head->next;ListNode* nex = nullptr;while(cur){nex = cur->next;if(cur->val == pre->val){pre->next = nex;delete cur;cur = nex;}else{pre = cur;cur = nex;}}return head;}
};

82. Remove Duplicates from Sorted List II

 

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* deleteDuplicates(ListNode* head) {if(head == nullptr)return head;ListNode* dummy = new ListNode(-1,head);ListNode* prepre = dummy;int pre_val = head->val;ListNode* pre = head;ListNode* cur = pre->next;ListNode* nex = nullptr;while(cur){nex = cur->next;if(cur->val == pre_val){prepre->next = nex;if(pre){delete pre;pre = nullptr;}delete cur;cur = nex;}else{if(pre){prepre = pre;}pre = cur;pre_val = pre->val;cur = nex;}}ListNode* ans = dummy->next;delete dummy;return ans;}
};

1836. Remove Duplicates From an Unsorted Linked List

 

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* deleteDuplicatesUnsorted(ListNode* head) {unordered_map<int,int> count;ListNode* cur = head;while(cur){count[cur->val]++;cur = cur->next;}ListNode* dummy = new ListNode(-1,head);ListNode* pre = dummy;cur = head;ListNode* post = nullptr;while(cur){post = cur->next;if(count[cur->val] > 1){pre->next = post;// delete cur;cur = post;}else{pre = cur;cur = post;}}ListNode* ans = dummy->next;delete dummy;return ans;}
};