LeetCode-56. Merge Intervals

Description

Given a collection of intervals, merge all overlapping intervals.
           

Example 1

Input: [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [,] and [,] overlaps, merge them into [,].
           

Example 2

Input: [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [,] and [,] are considerred overlapping.
           

Solution 1(C++)

class Solution {
public:
    vector<Interval> merge(vector<Interval>& ins) {
        if (ins.empty()) return vector<Interval>{};
        vector<Interval> res;
        sort(ins.begin(), ins.end(), [](Interval a, Interval b){return a.start < b.start;});
        res.push_back(ins[]);
        for (int i = ; i < ins.size(); i++) {
            if (res.back().end < ins[i].start) res.push_back(ins[i]);
            else
                res.back().end = max(res.back().end, ins[i].end);
        }
        return res;
    }
};
           

算法分析

我最開始打算兩層周遊，但是很明顯做複雜了，這樣還不如先排序，然後就好做多了，關鍵就是如何排序。利用sort函數與Lambda表達式，可參考：

• C++—— Lambda表達式

程式分析

Lambda表達式：

sort(ins.begin(), ins.end(), [](Interval a, Interval b){return a.start < b.start;});