LeetCode:Merge Intervals

Merge Intervals

Total Accepted: 71689 Total
Submissions: 275494 Difficulty: Hard

Given a collection of intervals, merge all overlapping intervals.
For example,

Given

[1,3],[2,6],[8,10],[15,18]

,

return

[1,6],[8,10],[15,18]

.

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思路：

用开始时间排个序，维护两个值start、end，然后判断“上一个集合”的结束时间与“下一个集合”开始时间时否交叉，交叉则合并；

不交叉则重设start、end值。

java code:

/**
* Definition for an interval.
* public class Interval {
*     int start;
*     int end;
*     Interval() { start = 0; end = 0; }
*     Interval(int s, int e) { start = s; end = e; }
* }
*/
public class Solution {
public List<Interval> merge(List<Interval> intervals) {

List<Interval> result = new ArrayList<>();
if(intervals == null || intervals.size() == 0) return result;

Collections.sort(intervals, new Comparator<Interval>(){
@Override
public int compare(Interval val1, Interval val2) {
return Integer.compare(val1.start, val2.start);
}
});

int start = intervals.get(0).start;
int end = intervals.get(0).end;

for(Interval val: intervals) {
if(val.start <= end) {
end = Math.max(end, val.end);
}else{
result.add(new Interval(start, end));
start = val.start;
end = val.end;
}
}
result.add(new Interval(start, end));
return result;
}
}