[LeetCode]Merge Intervals

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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].

参照insert intervals

/** * 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> res = new ArrayList<>();    for(int i=0;i<intervals.size();i++){    res=insert(res,intervals.get(i));    }        return res;    }    private List<Interval> insert(List<Interval> intervals, Interval newInterval) {    List<Interval> list = new ArrayList<Interval>();    if(intervals.size()==0){    list.add(newInterval);    return list;    }int start = newInterval.start;int end = newInterval.end;int mstart=-1;int mend=-1;int nstart = -1;int nend = -1;for(int i=0;i<intervals.size();i++){Interval in = intervals.get(i);Interval next = null;if(i!=intervals.size()-1) {next= intervals.get(i+1);}if(in.start<=start&&start<=in.end){mstart = i;nstart = in.start;break;}else if(i!=intervals.size()-1&&in.end<start&&start<next.start){mstart = i+1;nstart = start;break;}}for(int i=0;i<intervals.size();i++){Interval in = intervals.get(i);Interval next = null;if(i!=intervals.size()-1) {next= intervals.get(i+1);}if(in.start<=end&&end<=in.end){mend = i;nend = in.end;break;}else if(i!=intervals.size()-1&&in.end<end&&end<next.start){mend = i;nend = end;break;}}if(mstart==-1&&mend ==-1){if(start>intervals.get(intervals.size()-1).end){list = intervals;list.add(newInterval);}else if(end<intervals.get(0).start){list = intervals;list.add(0, newInterval);}else{list.add(newInterval);}return list;}else if(mstart==-1){mstart = 0;nstart = start;list = intervals.subList(mend+1, intervals.size());list.add(0,new Interval(nstart,nend));return list;}else if(mend == -1){mend = list.size()-1;nend = end;list = intervals.subList(0, mstart);list.add(new Interval(nstart,nend));return list;}list.addAll(intervals.subList(0, mstart));list.add(new Interval(nstart,nend));list.addAll(intervals.subList(mend+1, intervals.size()));return list;    }}

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