83. Remove Duplicates from Sorted List

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83. Remove Duplicates from Sorted List

Description

Difficulty: Easy

Related Topics: Linked List

Given the head of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well.

Example 1:

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

Example 2:

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

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.

Hints/Notes

  • Fast/slow pointers
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class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        return nullptr;
    }
}

Solution

Language: C++

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/**
 * 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) return head;
        ListNode* slow = head, *fast = head;
        while (fast) {
            while (fast && fast->val == slow->val) {
                fast = fast->next;
            }
            slow->next = fast;
            slow = slow->next;
        }
        return head;
    }
};