leetCode-My Calendar I

Description:
Implement a MyCalendar class to store your events. A new event can be added if adding the event will not cause a double booking.

Your class will have the method, book(int start, int end). Formally, this represents a booking on the half open interval [start, end), the range of real numbers x such that start <= x < end.

A double booking happens when two events have some non-empty intersection (ie., there is some time that is common to both events.)

For each call to the method MyCalendar.book, return true if the event can be added to the calendar successfully without causing a double booking. Otherwise, return false and do not add the event to the calendar.
Your class will be called like this: MyCalendar cal = new MyCalendar(); MyCalendar.book(start, end)

Example 1:

MyCalendar();MyCalendar.book(10, 20); // returns trueMyCalendar.book(15, 25); // returns falseMyCalendar.book(20, 30); // returns trueExplanation: The first event can be booked.  The second can't because time 15 is already booked by another event.The third event can be booked, as the first event takes every time less than 20, but not including 20.

Note:
The number of calls to MyCalendar.book per test case will be at most 1000.
In calls to MyCalendar.book(start, end), start and end are integers in the range [0, 10^9].

My Solution:

class MyCalendar {    List<List<Integer>> list;    public MyCalendar() {        list = new ArrayList<List<Integer>>();    }    public boolean book(int start, int end) {        int len  = list.size();        for(int i = 0;i < len;i++){            List<Integer> line = list.get(i);            int x = line.get(0);            int y = line.get(1);            if(!(start >= y || end <= x)){                return false;            }        }        List<Integer> line = new ArrayList<Integer>();        line.add(start);        line.add(end);        list.add(line);        return true;    }}

Better Solution:

//思想是找到比end小的最大bstart(已预订)，然后判断tm.get(s)（即bstart对应的bend）是否大于start,如果大于,说明时间相交，否则不相交class MyCalendar {    TreeMap<Integer, Integer> tm = new TreeMap<Integer, Integer>();    public MyCalendar() {    }    public boolean book(int start, int end) {    //lowerkey()找到比end小的最大key        Integer s = tm.lowerKey(end);        if(s!=null){            int e = tm.get(s);            if(e>start){                return false;            }        }        tm.put(start, end);        return true;    }}