435. 无重叠区间

class Solution 
{
public:
    int eraseOverlapIntervals(vector<vector<int>>& intervals) 
    {
        if(intervals.empty() || intervals[0].empty()) return 0;
        sort(intervals.begin(),intervals.end());

        int begin = intervals[0][0],end = intervals[0][1];
        int count = 0;
        for(int i = 1;i < intervals.size();i ++)
        {
            if(intervals[i][1] < end) 
            {
                begin = intervals[i][0];
                end = intervals[i][1];
                count ++;
            }
            else if(intervals[i][1] >= end && intervals[i][0] < end)
            {
                begin = intervals[i][0];
                count ++;
            } //区间[1,2]和[2,3]的边界相互“接触”，但没有相互重叠
            else if(intervals[i][0] >= end)
            {
                begin = intervals[i][0];
                end = intervals[i][1];
            }
        }
        return count;
    }
};