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[20220829] leetcode study-plan 문제 풀이

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	`1`	`+# https://leetcode.com/problems/linked-list-cycle-ii/`
	`2`	`+# 142. Linked List Cycle II`
	`3`	`+`
	`4`	`+from typing import Optional`
	`5`	`+from common.leetcodeds import ListNode`
	`6`	`+`
	`7`	`+`
	`8`	`+# Definition for singly-linked list.`
	`9`	`+# class ListNode:`
	`10`	`+# def __init__(self, x):`
	`11`	`+# self.val = x`
	`12`	`+# self.next = None`
	`13`	`+`
	`14`	`+class Solution:`
	`15`	`+ def detectCycle(self, head: Optional[ListNode]) -> Optional[ListNode]:`
	`16`	`+ if head is None:`
	`17`	`+ return None`
	`18`	`+ slow, fast = head, head`
	`19`	`+ cycle = False`
	`20`	`+`
	`21`	`+ while fast is not None and fast.next is not None:`
	`22`	`+ slow = slow.next`
	`23`	`+ fast = fast.next.next`
	`24`	`+`
	`25`	`+ if slow == fast:`
	`26`	`+ cycle = True`
	`27`	`+ break`
	`28`	`+`
	`29`	`+ if not cycle:`
	`30`	`+ return None`
	`31`	`+`
	`32`	`+ while head != slow:`
	`33`	`+ head = head.next`
	`34`	`+ slow = slow.next`
	`35`	`+ return slow`
	`36`	`+`
	`37`	`+`
	`38`	`+if __name__ == '__main__':`
	`39`	`+ node = ListNode(3)`
	`40`	`+ node.next = ListNode(2)`
	`41`	`+ node.next.next = ListNode(0)`
	`42`	`+ node.next.next.next = ListNode(-4)`
	`43`	`+ node.next.next.next.next = node.next`
	`44`	`+ sol = Solution()`
	`45`	`+ print(sol.detectCycle(node))`

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	`1`	`+# https://leetcode.com/problems/middle-of-the-linked-list/`
	`2`	`+# 876. Middle of the Linked List`
	`3`	`+`
	`4`	`+from typing import Optional`
	`5`	`+from common.leetcodeds import ListNode`
	`6`	`+`
	`7`	`+`
	`8`	`+# Definition for singly-linked list.`
	`9`	`+# class ListNode:`
	`10`	`+# def __init__(self, x):`
	`11`	`+# self.val = x`
	`12`	`+# self.next = None`
	`13`	`+`
	`14`	`+`
	`15`	`+class Solution:`
	`16`	`+ def middleNode(self, head: Optional[ListNode]) -> Optional[ListNode]:`
	`17`	`+ first, second = head, head`
	`18`	`+`
	`19`	`+ if head.next is None:`
	`20`	`+ return head`
	`21`	`+`
	`22`	`+ while second is not None and second.next is not None:`
	`23`	`+ first = first.next`
	`24`	`+ second = second.next.next`
	`25`	`+`
	`26`	`+ return first`
	`27`	`+`

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