56.Merge Intervals

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].

这里先排序，然后在合并，只要想到了先排序，这道题就好做了，运用STL中sort函数，然后自己写个比较大小的重载函数.

/**
 * 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:
    static bool cmp(const Interval&a,const Interval&b)
    {
        return a.start<b.start;
    }
    vector<Interval> merge(vector<Interval>& intervals) {
        if(intervals.size()==0||intervals.size()==1)
            return intervals;
        sort(intervals.begin(),intervals.end(),cmp);
        vector<Interval> res;
        res.push_back(intervals[0]);
        for(int i=1;i<intervals.size();i++)
        {
            Interval temp=res.back();
            if(temp.end>=intervals[i].start&&temp.end<intervals[i].end)
            {
                 temp.end=intervals[i].end;
                 res.pop_back();
                 res.push_back(temp);
            }
               
            else if(temp.end<intervals[i].start)
                res.push_back(intervals[i]);
        }
        return res;
    }
};

 

New impl(2021/0613)

class Solution {
public:
    static bool cmp(vector<int> a, vector<int> b)
    {
        return a[0] < b[0];
    }
    vector<vector<int>> merge(vector<vector<int>>& intervals) {
        sort(intervals.begin(), intervals.end(), cmp);
        int len = intervals.size();
        vector<vector<int>> res;
        if(len < 1 )
        {
            return res;
        }

        int i = 0;
        while(i < len)
        {
            vector<int > temp = intervals[i];
            i++;
            while(i<len && intervals[i][0] <= temp[1])
            {
                temp[1] = max(intervals[i][1],temp[1]);
                i++;
            }
            res.push_back(temp);
        }
        return res;
    }
};