排序后迭代，遇到符合条件的就删除前一项，合并到后一项。

class Solution {
public:vector<vector<int>> merge(vector<vector<int>>& intervals) {int left = 0,right = 0;sort(intervals.begin(), intervals.end());vector<int> tmp;for(auto it = intervals.begin(); it != --(intervals.end()); ){if((*it)[1] >= (*(++it))[0]){left = (*(--it))[0];right = (*it)[1];it = intervals.erase(it);right = max(right,(*it)[1]);tmp.push_back(left);tmp.push_back(right);*(it) = tmp;tmp.clear();}}return intervals;}
};