public ListNode rotateRight(ListNode head, int k) {
if (head == null) {
return head;
}
int n = k;
int listSize = 0;
ListNode end = head;
while (k > 0) {
end = end.next;
k--;
listSize++;
if (end == null) {
k = n % listSize;
end = head;
while (k > 0) {
end = end.next;
k--;
}
break;
}
}
if (head == end) {
return head;
}
ListNode start = head;
while (end.next != null) {
end = end.next;
start = start.next;
}
end.next = head;
head = start.next;
start.next = null;
return head;
}
private void zip(ListNode l1, ListNode l2) {
while (l2 != null) {
ListNode temp = l1.next;
l1.next = l2;
l1 = temp;
temp = l2.next;
l2.next = l1;
l2 = temp;
}
}
private ListNode reverse(ListNode head) {
ListNode pre = null;
ListNode p = head;
while (p != null) {
ListNode temp = p.next;
p.next = pre;
pre = p;
p = temp;
}
return pre;
}
private ListNode[] split(ListNode head) {
ListNode[] lists = new ListNode[2];
lists[0] = head;
if (head == null || head.next == null) {
return lists;
}
ListNode slow = head;
ListNode fast = head.next.next;
while (fast != null) {
slow = slow.next;
if (fast.next == null) {
break;
}
fast = fast.next.next;
}
lists[1] = slow.next;
slow.next = null;
return lists;
}
/**
* 1. get catch point with two points(fast/slow) 2. split the cycle on that point 3. get the
* intersection/joint node
*
* <p>如果允许修改每个node的val，可以用染色的方法 node = head while(node != null) { node.val = 999999;
* if(node.next.val == 999999) return node.next; }
*
* @param head
* @return
*/
public ListNode detectCycle(ListNode head) {
if (head == null || head.next == null) return null;
LC_141_DetectCycle detector = new LC_141_DetectCycle();
ListNode p = detector.getCatchPoint(head);
if (p == null) return null;
// split the cycle on the catch point, then get the intersection node
ListNode head2 = p.next;
p.next = null;
LC_160_GetIntersectionNode inst = new LC_160_GetIntersectionNode();
return inst.getIntersectionNode(head, head2);
// another way is a little magic
// suppose the distance between head and joint point is K, then it can be
// proved that the catch point is also K distance far from the joint.
/*
ListNode p1 = head;
while(p1 != p) {
p1 = p1.next;
p = p.next;
}
return p;
*/
}
public ListNode partition(ListNode head, int x) {
ListNode lessHead = null;
ListNode lessTail = null;
ListNode greaterHead = null;
ListNode greaterTail = null;
ListNode p = head;
while (p != null) {
if (p.val < x) {
if (lessHead == null) {
lessHead = p;
} else {
lessTail.next = p;
}
lessTail = p;
} else {
if (greaterHead == null) {
greaterHead = p;
} else {
greaterTail.next = p;
}
greaterTail = p;
}
p = p.next;
}
if (lessHead == null) {
if (greaterTail != null) {
greaterTail.next = null;
}
return greaterHead;
} else {
lessTail.next = greaterHead;
if (greaterTail != null) {
greaterTail.next = null;
}
return lessHead;
}
}
public static void main(String[] args) {
ListNode n1 = new ListNode(1);
ListNode n2 = new ListNode(2);
ListNode n3 = new ListNode(3);
ListNode n4 = new ListNode(4);
ListNode n5 = new ListNode(5);
ListNode n6 = new ListNode(6);
n1.next = n2;
n2.next = n3;
n3.next = n4;
n4.next = n5;
n5.next = n6;
n6.next = n3;
LC_141_DetectCycle inst = new LC_141_DetectCycle();
System.out.println(inst.hasCycle(n1));
}