82. Remove Duplicates from Sorted List II

Medium (Trung bình) C++ 🔗 Xem trên LeetCode

📋 Đề Bài

Given the head of a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. Return the linked list sorted as well.

Example 1:

Input: head = [1,2,3,3,4,4,5]
Output: [1,2,5]

Example 2:

Input: head = [1,1,1,2,3]
Output: [2,3]

Constraints:

The number of nodes in the list is in the range [0, 300].
-100 <= Node.val <= 100
The list is guaranteed to be sorted in ascending order.

🧠 Thuật Toán & Kỹ Thuật

Linked List (Danh sách liên kết)

⏱️ Thời gian O(n²)

💾 Không gian O(n)

💻 Lời Giải

C++ 0082-remove-duplicates-from-sorted-list-ii.cpp

/**
 * 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) {
        map<int, int> um;
        ListNode *currNode = head;
        
        while (currNode) {
            um[currNode->val]++;
            currNode = currNode->next;
        }
        
        ListNode *newNode = new ListNode(0);
        ListNode *tmpNode = newNode;
        
        for (auto [key, val] : um) {
            if (val > 1) {
                continue;
            }
            tmpNode->next = new ListNode(key);
            tmpNode = tmpNode->next;
        }
        
        return newNode->next;
    }
};