Merge Intervals

题目

原题

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

先排序后merge

code

/** * 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) {        /// here use '<' operator instead of '<=' operator        /// othwise, 'time limit exceeded' or 'runtime error' occurs!        /// i don't know why        return a.start < b.start;    }    vector<Interval> merge(vector<Interval>& intervals) {        int len = intervals.size();        if(len <= 1) return intervals;        /// sort -- use static member funtion        std::sort(intervals.begin(), intervals.end(), Solution::cmp);        /// init        vector<Interval> res;        /// method1        Interval tmp = intervals[0];        for(int i = 1; i < len; i++) {            if(tmp.end >= intervals[i].start) {                tmp.end = max(tmp.end, intervals[i].end);            } else {                res.push_back(tmp);                tmp.start = intervals[i].start;                tmp.end = intervals[i].end;            }        }        res.push_back(tmp);        /// method 2        // res.push_back(intervals[0]);        // for (int i = 1; i < intervals.size(); i++){        //     if (res.back().end >= intervals[i].start){        //         res.back().end = max(res.back().end, intervals[i].end);        //     }else{        //         res.push_back(intervals[i]);        //     }           // }        return res;    }};