Merge Intervals(sort)

Given a collection of intervals, merge all overlapping intervals.

Example 1:

Input:
 [[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:
 [[1,4],[4,5]]

Output:
 [[1,5]]

Explanation:
 Intervals [1,4] and [4,5] are considerred overlapping.

分析

这里不是拆interval，而是整个obj 排序

初始放第一个start and end. 结尾把最后start end加入

# Definition for an interval.
# class Interval:
#     def __init__(self, s=0, e=0):
#         self.start = s
#         self.end = e
from operator import itemgetter, attrgetter


class Solution:
    def merge(self, intervals):
        """
        :type intervals: List[Interval]
        :rtype: List[Interval]
        """
        if not intervals:
            return intervals

        # intervals.sort(key=attrgetter('start', 'end'))
        intervals.sort(key=lambda Interval:(Interval.start, Interval.end))
        start, end = intervals[0].start, intervals[0].end
        res = []
        for i in intervals[1:]:
            if i.start > end:
                res.append(Interval(start, end))
                start = i.start
                end = i.end

            if i.end > end:
                end = i.end
        res.append(Interval(start, end))

        return res

注意sort key

只和res里最后一个end比较，或者加入res ，或者改end

# Definition for an interval.
# class Interval:
#     def __init__(self, s=0, e=0):
#         self.start = s
#         self.end = e

class Solution:
    def merge(self, intervals):
        """
        :type intervals: List[Interval]
        :rtype: List[Interval]
        """
        intervals.sort(key = lambda i:i.start)
        res = []
        for i in intervals:
            if res and i.start<=res[-1].end:
                res[-1].end = max(i.end,res[-1].end)
            else:
                res.append(i)
        return res

/**
 * 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; }
 * }
 */
class Solution {
    public List<Interval> merge(List<Interval> intervals) {
        if(intervals.size() <= 1)
            return intervals;
        List<Interval> ret = new ArrayList<Interval>();
        intervals.sort((i1, i2) -> Integer.compare(i1.start, i2.start));
        int start = intervals.get(0).start;
        int end = intervals.get(0).end;
        for(Interval i : intervals){
            if(i.start <= end){
                end = Math.max(end, i.end);
            }else{
                ret.add(new Interval(start, end));
                start = i.start;
                end = i.end;
            }
        }
        ret.add(new Interval(start, end));//还要加上最后一个interval
        return ret;
    }
}