56. Merge Intervals

• Total Accepted: 105470
• Total Submissions: 367141
• Difficulty: Medium
• Contributors: Admin

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].

来源： https://leetcode.com/problems/merge-intervals/

分析

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首先将给定的intervals排序，按照首元素 accending order 排序

然后遍历合并。实践复杂度 O(NlogN)

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/**  * Definition for an interval.  * struct Interval {  *     int start;  *     int end;  *     Interval() : start(0), end(0) {}  *     Interval(int s, int e) : start(s), end(e) {}  * };  */ class Solution { public:     struct compare{         bool operator()(Interval a, Interval b){             return a.start < b.start;         }     }myCompare;           vector<Interval> merge(vector<Interval>& intervals) {         sort(intervals.begin(), intervals.end(), myCompare);         vector<Interval> results;         for(auto i: intervals){             if(!results.empty() && i.start <= results.back().end){                 results.back().end = max(i.end, results.back().end);             }             else{                 results.push_back(i);             }         }         return results;     } };

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