LeetCode Problem
56. Merge Intervals
Link to 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] overlap, merge them into [1,6].
Analysis
The key to solve this problem is defining a Comparator first to sort the arraylist of Intevals.
public List< Interval> merge(List intervals) {
if(intervals == null || intervals.size()<=1){
return intervals;
}
Collections.sort(intervals, Comparator.comparing((Interval itl)->itl.start));
List result = new ArrayList<>();
Interval t = intervals.get(0);
for(int i=1; i< intervals.size(); i++){
Interval c = intervals.get(i);
if(c.start <= t.end){
t.end = Math.max(t.end, c.end);
}else{
result.add(t);
t = c;
}
}
result.add(t);
return result;
}