public class ListIntersection {// two single listpublic boolean isIntersectionOfTwoSingleList(ListNode l1, ListNode l2) {if (l1 == null || l2 == null) {return false;}// whether the end of two list is sameListNode endOfList1 = getEndOfList(l1);ListNode endOfList2 = getEndOfList(l2);return endOfList1 == endOfList2;}private ListNode getEndOfList(ListNode head) {if (head == null) {return null;}ListNode node = head;while (node.next != null) {node = node.next;}return node;}// two list with cyclepublic boolean isIntersectionOfTwoListWithCycle(ListNode l1, ListNode l2) {if (l1 == null || l2 == null) {return false;}ListNode slow = l1, fast = l2;while (fast.next != null || fast != null || slow != null) {slow = slow.next;fast = fast.next.next;if (slow == fast) {return true;}}return false;}
}

public class ListIntersection2 {// two single listpublic ListNode getFirstIntersectionNodeOfSingleList(ListNode l1,ListNode l2) {ListNode longNode = l1, shortNode = l2;int len1 = getLenOfList(l1);int len2 = getLenOfList(l2);if (len1 < len2) {longNode = l2;shortNode = l1;}int diff = Math.abs(len1 - len2);// long move diff stepswhile (diff > 0) {longNode = longNode.next;--diff;}while (longNode != null && shortNode != null) {if (longNode == shortNode) {return longNode;}longNode = longNode.next;shortNode = shortNode.next;}return null;}private int getLenOfList(ListNode head) {ListNode node = head;int len = 0;while (node != null) {++len;node = node.next;}return len;}// two list with cyclepublic ListNode getFirstIntersectionNodeOfCycleList(ListNode l1, ListNode l2) {if (l1 == null || l2 == null) {return null;}ListNode slow = l1, fast = l2;while (fast.next != null || fast != null || slow != null) {if (fast == slow) {break;}slow = slow.next;fast = fast.next.next;}if (fast == null || slow == null) {return null;}slow = l1;while (slow != fast) {slow = slow.next;fast = fast.next;}return slow;}
}