[数据结构与算法]【LeetCode】83 and 27（原地修改数组的算法题）

双指针之快慢指针，即维护两个移动规则不同的指针，一快一慢，当快指针满足指定条件时，对慢指针内容进行更新。常用于回环问题和原地修改数组算法题。

83. 删除排序链表中的重复元素

解法：快慢指针

# 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: ListNode) -> ListNode:
        # if not head:
        #     return head
        slow, fast = head, head
        while fast != None:
            if fast.val != slow.val:
                slow.next = fast
                slow = fast
                slow.next = None
            fast = fast.next
        # slow.next = None
        return head

27. 移除元素

解法：快慢指针

class Solution:
    def removeElement(self, nums: List[int], val: int) -> int:
        slow, fast = 0, 0
        while fast < len(nums):
            if nums[fast] != val:
                nums[slow] = nums[fast]
                slow += 1
            fast += 1
        # print(slow)
        return slow