83. Remove Duplicates from Sorted List.md

83. Remove Duplicates from Sorted List

1. Description

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:

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

Example 2:

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.

2. Solutions

Solution 1: Language: C Delete Nodes in $O(n)$

• Saturday, 07 August, 2021
• Time Complexity: $O(n)$
• Space Complexity: $O(1)$
• Runtime: 4 ms, faster than 93.35% of C online submissions for Remove Duplicates from Sorted List.
• Memory Usage: 6.4 MB, less than 68.84% of C online submissions for Remove Duplicates from Sorted List.

Refer to 237. Delete Node in a Linked List.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */

struct ListNode *deleteDuplicates(struct ListNode *head) {
    struct ListNode *curr = head;
    while (curr != NULL && curr->next != NULL) {
        if (curr->val == curr->next->val) {
            curr->next = curr->next->next;
        } else {
            curr = curr->next;
        }
    }
    return head;
}

Questions

1. If we need to free deleted nodes?