leetcode-linked list

83. Remove Duplicates from Sorted List.py

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    """
    
    we need two pointers called prev and cur
        -Initially, cur is one step forward to prev pointer.
        -Logic
        if prev.val == cur.val:
            prev.next = cur.next
            cur = cur.next
        else:
            prev = prev.next
            cur = cur.next
    
    d->1->1->1->2
   prev cur
    
    return d->1->2
    
    
    d->1->1
    
    return d->1
    """
    def deleteDuplicates(self, head: ListNode) -> ListNode:
        if not head:
            return head
        
        d = ListNode(None)
        d.next = head
        prev = d
        cur = d.next
        while cur:
            if prev.val == cur.val:
                prev.next = cur.next
                cur = cur.next
            else:
                prev = prev.next
                cur = cur.next
        return d.next