Problem

Given a sorted linked list, delete all duplicates such that each element appear only once.

Example 1:

Input: 1->1->2

Output: 1->2

Example 2:

Input: 1->1->2->3->3

Output: 1->2->3

Pre analysis

Will keep iterator, and move to next if next value is not same, else will point next to hopped next. Time Complexity: O(n) and space Complexity: O(1)

Another solution

Another fast-slow approach

var deleteDuplicates = function(head) {
    if(head === null) return head;

    var slower = head;
    var faster = head.next;
    while(slower !== null){
        while(faster !== null && faster.val == slower.val)
            faster = faster.next;
        slower.next = faster;
        slower = slower.next
        faster = slower !== null? slower.next : null;
    }
    return head;
};