leetcode -- Merge Intervals

关键不是怎么想，而是怎么做

 [问题描述]

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].

[解题思路]

排序 + 比较

bool cmp_Interval(Interval a, Interval b)
{
    return a.start == b.start?(a.end < b.end):(a.start < b.start);
}
class Solution {
public:
    vector<Interval> merge(vector<Interval> &intervals) {
        std::vector<Interval> ans;
        if (intervals.size() == 0)
            return ans;
        std::sort(intervals.begin(), intervals.end(), cmp_Interval);
        ans.push_back(intervals[0]);
        for (int i = 0; i < intervals.size(); i ++){
            if (ans[ans.size() - 1].end >= intervals[i].start)
                ans[ans.size() - 1].end = std::max(ans[ans.size() - 1].end, intervals[i].end);
            else
                ans.push_back(intervals[i] );
        }
        return ans;
    }
};