Find closest number in array

Given an array of sorted integers. We need to find the closest value to the given number. Array may contain duplicate values and negative numbers.

Examples:

Input : arr[] = {1, 2, 4, 5, 6, 6, 8, 9}
             Target number = 11
Output : 9
9 is closest to 11 in given array

Input :arr[] = {2, 5, 6, 7, 8, 8, 9}; 
       Target number = 4
Output : 5

simple solution is to traverse through the given array and keep track of absolute difference of current element with every element. Finally return the element that has minimum absolution difference.

An efficient solution is to use Binary Search.

// Java program to find element closet to given target.
import java.util.*;
import java.lang.*;
import java.io.*;
class FindClosestNumber {
    
    // Returns element closest to target in arr[]
    public static int findClosest(int arr[], int target)
    {
        int n = arr.length;
        // Corner cases
        if (target <= arr[0])
            return arr[0];
        if (target >= arr[n - 1])
            return arr[n - 1];
        // Doing binary search
        int i = 0, j = n, mid = 0;
        while (i < j) {
            mid = (i + j) / 2;
            if (arr[mid] == target)
                return arr[mid];
            /* If target is less than array element,
               then search in left */
            if (target < arr[mid]) {
       
                // If target is greater than previous
                // to mid, return closest of two
                if (mid > 0 && target > arr[mid - 1])
                    return getClosest(arr[mid - 1],
                                  arr[mid], target);
                
                /* Repeat for left half */
                j = mid;             
            }
            // If target is greater than mid
            else {
                if (mid < n-1 && target < arr[mid + 1])
                    return getClosest(arr[mid],
                          arr[mid + 1], target);               
                i = mid + 1; // update i
            }
        }
        // Only single element left after search
        return arr[mid];
    }
    // Method to compare which one is the more close
    // We find the closest by taking the difference
    //  between the target and both values. It assumes
    // that val2 is greater than val1 and target lies
    // between these two.
    public static int getClosest(int val1, int val2,
                                         int target)
    {
        if (target - val1 >= val2 - target)
            return val2;       
        else
            return val2;       
    }
    // Driver code
    public static void main(String[] args)
    {
        int arr[] = { 1, 2, 4, 5, 6, 6, 8, 9 };
        int target = 11;
        System.out.println(findClosest(arr, target));
    }
}

Output:

9

Disclaimer: This does not belong to TechCodeBit, its an article taken from the below
source and credits.
source and credits:http://www.geeksforgeeks.org/find-closest-number-array/
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rakesh

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