Leetcode:56. Merge Intervals

Description

Given a collection of intervals, merge all overlapping intervals.

Example

For example,

Given [1,3],[2,6],[8,10],[15,18],

return [1,6],[8,10],[15,18].

思路

• 先按照start从小到大排序，然后遍历一遍，找出新的区间

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> res;
        int len = intervals.size();
        if(len == 0) return res;
        
        sort(intervals.begin(), intervals.end(), 
            [](const Interval &a, const Interval &b){
                if(a.start != b.start)
                    return a.start < b.start;
                else return a.end < b.end;
            });
            
        int i = 0;
        while(i < len){
            Interval tmp;
            tmp.start = intervals[i].start;
            tmp.end = intervals[i].end;
            
            while(i + 1 < len && intervals[i + 1].start <= tmp.end){
                tmp.end = max(tmp.end, intervals[i + 1].end);
                i++;
            }
            
            res.push_back(tmp);
            i++;
        }
        
        return res;
    }
};