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].

• 按开始位置大小排序
• 循环数组；如果当前区间的开始位置大于上一个区间的结束位置，将上一个区间加入到答案里面；否则，将当前区间与上一个区间合并

/**
 * 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(const Interval &a,const Interval &b)
{
    return a.start < b.start;
}
class Solution
{
public:
    vector<Interval> merge(vector<Interval>& intervals)
    {
        vector<Interval> ans;
        if(intervals.size() == 0)
            return ans;
        
        sort(intervals.begin(), intervals.end(), cmp);
        
        int b, e;
        for(int i=0; i<intervals.size(); ++ i)
        {
            if(i == 0)
                b = intervals[i].start, e = intervals[i].end;
            else
            {
                if(intervals[i].start > e)
                {
                    ans.push_back(Interval(b, e));
                    b = intervals[i].start, e = intervals[i].end;
                }
                else
                {
                    if(intervals[i].end > e)
                        e = intervals[i].end;
                }
            }
        }
        ans.push_back(Interval(b, e));
        return ans;
    }
};