20210422 consolidation interval

In array intervals Represents a set of intervals , The single interval is intervals[i] = [starti, endi] . Please merge all overlapping intervals , And return a non overlapping interval array , The array needs to cover exactly all the intervals in the input .
Example 1：

Input ：intervals = [[1,3],[2,6],[8,10],[15,18]]
Output ：[[1,6],[8,10],[15,18]]
explain ： Section [1,3] and [2,6] overlap , Combine them into [1,6].
Example 2：

Input ：intervals = [[1,4],[4,5]]
Output ：[[1,5]]
explain ： Section [1,4] and [4,5] Can be regarded as overlapping interval .

class Solution {
    
public:
    vector<vector<int>> merge(vector<vector<int>>& intervals) {
    
        vector<vector<int>> ans;
        
        int m = intervals.size();
        if(m == 0)
        {
    
            return ans;
        }
        
        
        for(int i = 0; i < m; i++)
        {
    
            int L = intervals[i][0];
            int R = intervals[i][0];
            
            if(!ans.size() || ans.back()[1] < L)
            {
    
                ans.push_back({
    L,R});
            }
            else
            {
    
                ans.back()[1] = max(ans.back()[1], R);
            }
        }
        
        return ans;
    }
    
 
};