|255|[Verify Preorder Sequence in Binary Search Tree](https://leetcode.com/problems/verify-preorder-sequence-in-binary-search-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_255.java) | O(n) | O(h) | Medium| Tree

|254|[Factor Combinations](https://leetcode.com/problems/factor-combinations/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_254.java) | O(nlogn) | O(nlogn) | Medium| Backtracking

|253|[Meeting Rooms II](https://leetcode.com/problems/meeting-rooms-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_253.java) | O(nlogn) | O(h) | Medium| Heap

|252|[Meeting Rooms](https://leetcode.com/problems/meeting-rooms/)|[Solution](../master/src/main/java/com/fishercoder/solutions/MeetingRooms.java) | O(nlogn) | O(1) | Easy

|252|[Meeting Rooms](https://leetcode.com/problems/meeting-rooms/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_252.java) | O(nlogn) | O(1) | Easy

|251|[Flatten 2D Vector](https://leetcode.com/problems/flatten-2d-vector/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_251.java)| O(1)|O(m*n)| Medium|

|250|[Count Univalue Subtrees](https://leetcode.com/problems/count-univalue-subtrees/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_250.java)| O(n)|O(h) | Medium| DFS

|249|[Group Shifted Strings](https://leetcode.com/problems/group-shifted-strings/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_249.java)| O(nlogn)| O(n)|

importjava.util.Collections;

importjava.util.Comparator;

importjava.util.List;

publicclassMeetingRooms {

publicclass_252 {

publicbooleancanAttendMeetings(Interval[]intervals) {

List<Interval>list =newArrayList();