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142.java
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142.java
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__________________________________________________________________________________________________
sample 0 ms submission
/**
* Definition for singly-linked list.
* class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public ListNode detectCycle(ListNode head) {
if (null == head || null == head.next)
return null;
ListNode p, q;
p = head.next;
q = head.next.next;
while (q != null && p != q) {
p = p.next;
if (q.next == null)
q = null;
else
q = q.next.next;
}
if (q == null)
return null;
p = head;
while (p != q) {
p = p.next;
q = q.next;
}
return p;
}
}
__________________________________________________________________________________________________
sample 31436 kb submission
/**
* Definition for singly-linked list.
* class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public ListNode detectCycle(ListNode head) {
ListNode root = new ListNode(0);
root.next = head;
ListNode p1 = root;
ListNode p2 = root;
ListNode p;
while (true) {
if (p1 != null && p1.next != null && p1.next.next != null) {
p1 = p1.next.next;
p2 = p2.next;
} else {
System.gc();
return null;
}
if (p1 == p2) {
p = p1;
break;
}
}
ListNode h = root;
while (true) {
h = h.next;
p = p.next;
if (h == p) {
System.gc();
return h;
}
}
}
}
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