[LeetCode] (medium) 658. Find K Closest Elements

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博客给出LeetCode题目链接，要求在有序数组中找出最接近给定整数x的k个元素，结果需升序排列，若有平局则优先选较小元素。还给出了相关注意事项，如k为正且小于数组长度等，涉及有序数组和二分查找。

https://leetcode.com/problems/find-k-closest-elements/

Given a sorted array, two integers k and x, find the kclosest elements to x in the array. The result should also be sorted in ascending order. If there is a tie, the smaller elements are always preferred.

Example 1:
Input: [1,2,3,4,5], k=4, x=3
Output: [1,2,3,4]
Example 2:
Input: [1,2,3,4,5], k=4, x=-1
Output: [1,2,3,4]
Note:

The value k is positive and will always be smaller than the length of the sorted array.
Length of the given array is positive and will not exceed 104
Absolute value of elements in the array and x will not exceed 104

有序数组，二分：

class Solution {
public:
    vector<int> findClosestElements(vector<int>& arr, int k, int x) {
        int lo = 0, hi = arr.size()-k;
        int mid;
        while(lo < hi){
            mid = (lo+hi)/2;
            if(abs(x-arr[mid]) > abs(x-arr[mid+k])) lo = mid+1;
            else hi = mid;
        }
        return vector<int>(arr.begin()+lo, arr.begin()+lo+k);
    }
};