leetcode 658找到k个最接近的元素

class Solution {
public:
    vector<int> findClosestElements(vector<int>& arr, int k, int x) {
        //查找，二分法找到那个数的lowerbound然后左右指针比较；O(logn+2k)
        vector<int>::iterator p=lower_bound(arr.begin(),arr.end(),x);
        if(p!=arr.begin() && *p != x) p--;
        vector<int> res;
        int len=arr.size();
        int l=p-arr.begin(),r=p-arr.begin();
        //cout<<l<<","<<r<<endl;
        while(r-l<k-1){
            if(l==0){
                r++;continue;
            }
            if(r==len-1){
                l--;continue;
            }
            if(arr[r+1]-x>=x-arr[l-1])
                l--;
            else
                r++;
        }
        for(int i=l;i<=r;i++)
            res.push_back(arr[i]);
        return res;
    }
};