Find the closest number in a sorted array.

To find the closest number to a target value x in a sorted array, employ binary search. The core idea is that after the binary search completes, the low pointer will indicate the smallest element greater than or equal to x, and the high pointer will indicate the largest element less than or equal to x. Compare the absolute differences between x and arr[low] and x and arr[high]. The element with the smaller difference is the closest. If x is found exactly during the search, that element is the closest.