LeetCode 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].

 

思路： 按照每个线段的start排序。 然后merge.

AC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) {}
 * };
 */
 bool cmp(Interval A, Interval B)
 {
     return A.start < B.start;
 }
class Solution {
public:
    vector<Interval> merge(vector<Interval>& intervals) {
        int n = intervals.size();
        vector<Interval> ret;
        if(n == 0) return ret;
        sort(intervals.begin(), intervals.end(), cmp);
        int s = intervals[0].start;
        int e = intervals[0].end;
        for(int i=1; i<n; i++)
        {
            if(intervals[i].start <= e)
            {
                e = max(e, intervals[i].end);
            }
            else 
            {
                ret.push_back( Interval(s,e) );
                s = intervals[i].start;
                e = intervals[i].end;
            }
        }
        ret.push_back( Interval(s,e) );
        return ret;
    }
};