LeetCode 715. Range Module

原题链接在这里：https://leetcode.com/problems/range-module/

题目：

A Range Module is a module that tracks ranges of numbers. Your task is to design and implement the following interfaces in an efficient manner.

• addRange(int left, int right) Adds the half-open interval [left, right), tracking every real number in that interval. Adding an interval that partially overlaps with currently tracked numbers should add any numbers in the interval [left, right) that are not already tracked.

• queryRange(int left, int right) Returns true if and only if every real number in the interval [left, right) is currently being tracked.

• removeRange(int left, int right) Stops tracking every real number currently being tracked in the interval [left, right).

Example 1:

addRange(10, 20): null
removeRange(14, 16): null
queryRange(10, 14): true (Every number in [10, 14) is being tracked)
queryRange(13, 15): false (Numbers like 14, 14.03, 14.17 in [13, 15) are not being tracked)
queryRange(16, 17): true (The number 16 in [16, 17) is still being tracked, despite the remove operation)

Note:

• A half open interval [left, right) denotes all real numbers left <= x < right.
• 0 < left < right < 10^9 in all calls to addRange, queryRange, removeRange.
• The total number of calls to addRange in a single test case is at most 1000.
• The total number of calls to queryRange in a single test case is at most 5000.
• The total number of calls to removeRange in a single test case is at most 1000.

题解：

Have a TreeMap to store existing interval, key is start of interval and value is end.

When adding range, get floor key of left, if key exists and its corresponding value >= left, then there is a merge, left = preKey.

get floor key of right, if key exists and it sorrsonding value >= right, then there is another merge, right = tm.get(nextKey).

Add the new range and clear the keys from (left, right].

When querry Range, just check if there is existing interval coverring [left, right].

When removing range, first get floor key of right, if it exists and value > right, then after removing, there is still some range left. Add new range [right, tm.get(nextKey)).

Do the similar to left. But we need to do right first, because we may change value of preKey if we do left first.

Then remove keys in range [left, right).

Time Complexity: addRange, O(nlogn). clear takes O(nlogn). queryRange, O(logn). removeRange, O(nlogn).

Space: O(n).

AC Java:

 1 class RangeModule {
 2     TreeMap tm;
 3     
 4     public RangeModule() {
 5         tm = new TreeMap<>();    
 6     }
 7     
 8     public void addRange(int left, int right) {
 9         if(left >= right){
10             return;
11         }
12         
13         Integer preKey = tm.floorKey(left);
14         if(preKey != null && tm.get(preKey) >= left){
15             left = preKey;
16         }
17         
18         Integer nextKey = tm.floorKey(right);
19         if(nextKey != null && tm.get(nextKey) >= right){
20             right = tm.get(nextKey);
21         }
22         
23         tm.put(left, right);
24         tm.subMap(left, false, right, true).clear();
25     }
26     
27     public boolean queryRange(int left, int right) {
28         Integer preKey = tm.floorKey(left);
29         if(preKey == null){
30             return false;
31         }
32         
33         return tm.get(preKey) >= right;
34     }
35     
36     public void removeRange(int left, int right) {
37         if(left >= right){
38             return;
39         }
40         
41         Integer nextKey = tm.floorKey(right);
42         if(nextKey != null && tm.get(nextKey) > right){
43             tm.put(right, tm.get(nextKey));
44         }
45         
46         Integer preKey = tm.floorKey(left);
47         if(preKey != null && tm.get(preKey) > left){
48             tm.put(preKey, left);
49         }
50         
51         tm.subMap(left, true, right, false).clear();
52     }
53 }
54 
55 /**
56  * Your RangeModule object will be instantiated and called as such:
57  * RangeModule obj = new RangeModule();
58  * obj.addRange(left,right);
59  * boolean param_2 = obj.queryRange(left,right);
60  * obj.removeRange(left,right);
61  */

类似Merge Intervals.