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]. http://leetcode.com/onlinejudge#question_56

leetcode_merge_intervals.cpp

/**
 * 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) {
    if (a.start != b.start)
        return a.start < b.start;
    else
        return a.end < b.end;
}

class Solution {
public:
    vector<Interval> merge(vector<Interval> &intervals) {
        vector<Interval> ans;
        int n = intervals.size();
        sort(intervals.begin(), intervals.end(), cmp);
        int pos = 0;
        while (pos < n) {
            int npos;
            int nend = intervals[pos].end;
            for (npos = pos + 1; npos < n; ++npos) {
                if (nend < intervals[npos].start) {
                    break;
                }
                if (nend < intervals[npos].end) {
                    nend = intervals[npos].end;
                }
            }
            Interval tmp(intervals[pos].start, nend);
            ans.push_back(tmp);
            pos = npos;
        }
        return ans;
    }
};