56. Merge Intervals

题目

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].

解析

题意：将一个Interval新结构进行合并
关键点在于每次比较用的是ret中的尾Interval。

代码

/**
 * 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:
    vector<Interval> merge(vector<Interval>& intervals) {
        vector<Interval> ret;
        if(!intervals.size()) return ret;
        sort(intervals.begin(),intervals.end(),[](Interval a,Interval b){return a.start<b.start;});
        ret.push_back(intervals[0]);
        for(int i=1;i<intervals.size();i++){
            if(ret.back().end<intervals[i].start) ret.push_back(intervals[i]);
            else
                ret.back().end=max(ret.back().end,intervals[i].end);
        }
        return ret;
    }
};