658. Find K Closest Elements

1. Find K Closest Elements Medium

Given a sorted array, two integers k and x, find the k closest 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

class Solution(object):
    def findClosestElements(self, arr, k, x):
        """
        :type arr: List[int]
        :type k: int
        :type x: int
        :rtype: List[int]
        """
        if arr==None:
            return None
        l, r = 0, len(arr) - 1
        while l <= r:
            mid = l + (r-l)//2
            if arr[mid] < x:
                l = mid + 1
            else:
                r = mid - 1

        while r - l < k:
            if l == 0: return arr[:k]
            if r == len(arr): return arr[-k:]
            if x - arr[l-1] <= arr[r] - x: 
                l -= 1
            else: 
                r += 1
        return arr[l:r]

start +（end – start）/ 2 与 （start + end）/ 2 的区别：
如果start或end的值或两者均为INT_MAX，将会导致整数溢出。

参考链接：
Why start + (end – start)/2 is preferrable method for calculating middle of an array over (start + end)/2 ?