linked list cycle II

fishercoder1534 · fishercoder1534 · commit bd9ce9254fe4 · 2016-11-26T11:03:52.000-08:00
diff --git a/MEDIUM/src/medium/LinkedListCycleII.java b/MEDIUM/src/medium/LinkedListCycleII.java
@@ -0,0 +1,23 @@
+package medium;
+
+import classes.ListNode;
+
+public class LinkedListCycleII {
+
+    public ListNode detectCycle(ListNode head) {
+        ListNode slow = head, fast = head;
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+            if ( slow == fast) {
+                ListNode slow2 = head;
+                while (slow2 != slow) {
+                    slow = slow.next;
+                    slow2 = slow2.next;
+                }
+                return slow;
+            }
+        }
+        return null;
+    }
+}
diff --git a/README.md b/README.md
@@ -87,6 +87,7 @@
 |157|[Read N Characters Given Read4](https://leetcode.com/problems/read-n-characters-given-read4/)|[Solution](../../blob/master/EASY/src/easy/ReadNCharactersGivenRead4.java)| O(n)|O(1) | Easy| 
 |155|[Min Stack](https://leetcode.com/problems/min-stack/)|[Solution](../../blob/master/EASY/src/easy/MinStack.java)| O(1)|O(n) | Easy| Stack
 |151|[Reverse Words in a String](https://leetcode.com/problems/reverse-words-in-a-string/)|[Solution](../../blob/master/MEDIUM/src/medium/ReverseWordsinaString.java)| O(n)|O(n) | Medium|
+|142|[Linked List Cycle II](https://leetcode.com/problems/linked-list-cycle-ii/)|[Solution](../../blob/master/MEDIUM/src/medium/LinkedListCycleII.java)| O(n)|O(1) | Medium| Linked List
 |141|[Linked List Cycle](https://leetcode.com/problems/linked-list-cycle/)|[Solution](../../blob/master/EASY/src/easy/LinkedListCycle.java)| O(n)|O(1) | Easy| Linked List
 |140|[Word Break II](https://leetcode.com/problems/word-break-ii/)|[Solution](../../blob/master/HARD/src/hard/WordBreakII.java)| ? |O(n^2) | Hard| Backtracking/DFS
 |139|[Word Break](https://leetcode.com/problems/word-break/)|[Solution](../../blob/master/MEDIUM/src/medium/WordBreak.java)| O(n^2)|O(n) | Medium| DP
