83 Remove Duplicates From Sorted List

Remove Duplicates from Sorted 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:

**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.

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

    if (head == NULL) {
        return head; 
    }
    struct ListNode* prev = head;
    struct ListNode* tmp = head;
    while (prev ->next != NULL && prev ->next -> next != NULL ) {
        tmp = prev -> next;
        if (prev -> val == tmp -> val) {
            prev -> next = tmp -> next;
            free(tmp);
        } else {
            prev = prev -> next;
        }
        //prev = prev -> next;
    }

    if (prev ->next != NULL && prev -> val == prev -> next -> val) {
        prev -> next = NULL;
    }

    return head;
}