二分查找

436. 寻找右区间

class Solution {
public:
    int binsearch(vector<vector<int>>& arr, int k){
        int l=0,r=arr.size()-1;
        if(k>arr[r][0])return -1;
        while(l<r){
            int mid=l+(r-l)/2;
            if(arr[mid][0]<k)l=mid+1;
            else
                r=mid;
        }
        return arr[l][1];
    }
    vector<int> findRightInterval(vector<vector<int>>& intervals) {
        vector<vector<int>> help=intervals;

        for(int i=0;i<intervals.size();i++){
            help[i][1]=i;
        }
        sort(help.begin(),help.end(),[](vector<int>& a,vector<int>& b){return a[0]<b[0];});
        vector<int> ans;
        for(int i=0;i<intervals.size();i++){
            ans.push_back(binsearch(help,intervals[i][1]));
        }
        return ans;
    }
};