[Leetcode] 83. Remove Duplicates from Sorted List

題目 : 83. 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]

1.

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def deleteDuplicates(self, head: Optional[ListNode]) -> Optional[ListNode]:
        # 將curr和temp指向head
        # curr是目前要比對的數字
        # temp是下一個要比對的數字
        curr = temp = head

        # 如果head是None直接回傳head
        if head == None:
            return head

        # temp因為是下一個要比對的數字，所以讓他指向下一個node
        temp = temp.next

        # 進入while迴圈，直到沒有下一個可以比對的node
        while temp != None:
            # 如果目前的node值(curr)和下一個node值(temp)一樣
            if curr.val == temp.val:
                # temp指向下一個node，繼續比對
                temp = temp.next
            else: # 如果目前的node值(curr)和下一個node值(temp)不一樣
                # 讓curr的下一個node指向temp
                curr.next = temp
                # 將temp和curr指向下一個node，繼續比對
                temp = temp.next
                curr = curr.next
                
        # 最後要將curr的下一個node指向None
        curr.next = None

        return head