82. Remove Duplicates from Sorted List II

Medium

Given the head of a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. Return the linked list sorted as well.

Example 1:

Input: head = [1,2,3,3,4,4,5]
Output:
 [1,2,5]

Example 2:

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

解題

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func deleteDuplicates(head *ListNode) *ListNode {
    if head==nil { return nil }
    
    fakeHead := &ListNode{ Next:head }
    
    pre := fakeHead
    cur := fakeHead.Next
    
    for cur!= nil {
        for cur.Next!=nil && cur.Val==cur.Next.Val {
            cur = cur.Next
        }
        
        if pre.Next == cur {
            pre = pre.Next
        } else {
            pre.Next = cur.Next
        }
        
        cur = cur.Next
    }
    
    
    return fakeHead.Next
}