LetCode 56. 合并区间

/**
 * 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;
}
static int x=[](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution {
public:
    vector merge(vector& intervals) {
        vector res;
        if (intervals.size() <= 0)
            return res;
        // 先以start从小到大开始排序
        sort(intervals.begin(), intervals.end(), cmp);
        int start = intervals[0].start;
        int end = intervals[0].end;
        // 如果此时的start小于当前的end，则合并到当前区间
        // 否则，当前区间重新开始计算
        for (int i = 1; i < intervals.size(); i++){
            if (intervals[i].start <= end)
                end = max(intervals[i].end, end);
            else{
                res.push_back(Interval(start, end));
                start = intervals[i].start;
                end = intervals[i].end;
            }
        }
        // 最后检查一下最后一个区间是否放进去了
        if (res.size() <= 0)
             res.push_back(Interval(start, end));
        else if (res[res.size() - 1].end < start)
             res.push_back(Interval(start, end));
        return res;
    }
};