排序56.合并区间

Leetcode

排序56.合并区间

给出一个区间的集合，请合并所有重叠的区间。
示例 1:
输入: intervals = [[1,3],[2,6],[8,10],[15,18]]
输出: [[1,6],[8,10],[15,18]]
解释: 区间 [1,3] 和 [2,6] 重叠, 将它们合并为 [1,6].

双指针法：

class Solution {
public:
    vector<vector<int>> merge(vector<vector<int>>& intervals) {
        vector<vector<int>> res;
        vector<int> starts,ends;
        for(int i=0;i<intervals.size();i++)
        {
            starts.push_back(intervals[i][0]);
            ends.push_back(intervals[i][1]);
        }
        sort(starts.begin(),starts.end());
        sort(ends.begin(),ends.end());
        for(int i=0,j=0;i<intervals.size();i++)
        {
            if(i==intervals.size()-1 || starts[i+1]>ends[i] )
            {
                res.push_back({starts[j],ends[i]});
                j = i+1;
            }
        }
        return res;
    }
};

先比较后排序

class Solution {
public:
    vector<vector<int>> merge(vector<vector<int>>& intervals) {
     if(intervals.empty())return{};
     sort(intervals.begin(),intervals.end());
     vector<vector<int>>res;
     res.push_back(intervals[0]);
     for(int i=1;i<intervals.size();i++)
     {
         if(res.back()[1]>=intervals[i][0])
         {
             res.back()[1] = max(res.back()[1],intervals[i][1]);
         }
         else
         {
             res.push_back(intervals[i]);
         }
     }
     return res;
    }
};