Leetcode 56. Merge Intervals

[medium]

Merge Intervals - LeetCode

Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.

Example 1:

Input: intervals = [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6].

Example 2:

Input: intervals = [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] are considered overlapping.

Constraints:

• 1 <= intervals.length <= 104
• intervals[i].length == 2
• 0 <= starti <= endi <= 104

[Java]

1. Need to use array sort to sort the open window
2. create datastructure List<int[]> to easy add the answer
3. compare all the intervals, if close window smaller or equal to current close winder, update to the max one
4. else update the current winder to the res list
5. change res back to array style