Commit c804312

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LC#142 find first meet point in linkedlist cycle - medium problem

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	`1`	`+package LinkedList;`
	`2`	`+`
	`3`	`+public class LinkedListCycleII142 {`
	`4`	`+`
	`5`	`+ class ListNode {`
	`6`	`+ int val;`
	`7`	`+ ListNode next;`
	`8`	`+`
	`9`	`+ ListNode(int x) {`
	`10`	`+ val = x;`
	`11`	`+ next = null;`
	`12`	`+ }`
	`13`	`+ }`
	`14`	`+`
	`15`	`+ public ListNode detectCycle(ListNode head) {`
	`16`	`+`
	`17`	`+ if (head == null \|\| head.next == null)`
	`18`	`+ return null;`
	`19`	`+`
	`20`	`+ ListNode ptr1 = head;`
	`21`	`+ ListNode ptr2 = detectCycle1(head);`
	`22`	`+`
	`23`	`+ if (ptr2 == null)`
	`24`	`+ return null;`
	`25`	`+`
	`26`	`+ while (ptr1 != ptr2) {`
	`27`	`+ ptr1 = ptr1.next;`
	`28`	`+ ptr2 = ptr2.next;`
	`29`	`+ }`
	`30`	`+`
	`31`	`+ return ptr1 == ptr2 ? ptr1 : null;`
	`32`	`+ }`
	`33`	`+`
	`34`	`+ private static ListNode detectCycle1(ListNode head) {`
	`35`	`+ if (head == null \|\| head.next == null)`
	`36`	`+ return null;`
	`37`	`+`
	`38`	`+ ListNode slow = head, fast = head;`
	`39`	`+`
	`40`	`+ while (fast != null && fast.next != null) {`
	`41`	`+ slow = slow.next;`
	`42`	`+ fast = fast.next.next;`
	`43`	`+`
	`44`	`+ if (slow == fast) {`
	`45`	`+ return fast;`
	`46`	`+ }`
	`47`	`+ }`
	`48`	`+ return null;`
	`49`	`+ }`
	`50`	`+}`

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