查找数组中最接近的数字

给定一个排序的整数数组。我们需要找到最接近给定数字的值。数组可能包含重复值和负数。

例子：

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

一个简单的解决方案是遍历给定的数组并跟踪当前元素与每个元素的绝对差。最后返回具有最小绝对值差的元素。

一个有效的解决方案是使用二进制搜索。

C++

// CPP program to find element
// closet to given target.
#include 
using namespace std;
  
int getClosest(int, int, int);
  
// Returns element closest to target in arr[]
int findClosest(int arr[], int n, int target)
{
    // 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);
            // update i
            i = mid + 1; 
        }
    }
  
    // 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.
int getClosest(int val1, int val2,
               int target)
{
    if (target - val1 >= val2 - target)
        return val2;
    else
        return val1;
}
  
// Driver code
int main()
{
    int arr[] = { 1, 2, 4, 5, 6, 6, 8, 9 };
    int n = sizeof(arr) / sizeof(arr[0]);
    int target = 11;
    cout << (findClosest(arr, n, target));
}
  
// This code is contributed bu Smitha Dinesh Semwal

Java

// 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 val1;        
    }
  
    // 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));
    }
}

Python 3

# Python3 program to find element
# closet to given target.
  
# Returns element closest to target in arr[]
def findClosest(arr, n, target):
  
    # Corner cases
    if (target <= arr[0]):
        return arr[0]
    if (target >= arr[n - 1]):
        return arr[n - 1]
  
    # Doing binary search
    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 and 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 and target < arr[mid + 1]):
                return getClosest(arr[mid], arr[mid + 1], target)
                  
            # update i
            i = mid + 1
          
    # 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.
def getClosest(val1, val2, target):
  
    if (target - val1 >= val2 - target):
        return val2
    else:
        return val1
  
# Driver code
arr = [1, 2, 4, 5, 6, 6, 8, 9] 
n = len(arr)
target = 11
print(findClosest(arr, n, target))
  
# This code is contributed by Smitha Dinesh Semwal

C#

// C# program to find element 
// closet to given target.
using System;
  
class GFG
{
      
    // 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 val1;     
    }
  
    // Driver code
    public static void Main()
    {
        int []arr = {1, 2, 4, 5, 
                     6, 6, 8, 9};
        int target = 11;
        Console.WriteLine(findClosest(arr, target));
    }
}
  
// This code is contributed by anuj_67.

PHP

= $arr[$n - 1]) 
        return $arr[$n - 1]; 
  
    // Doing binary search 
    $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); 
            // update i 
            $i = $mid + 1; 
        } 
    } 
  
    // 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. 
function getClosest($val1, $val2, $target) 
{ 
    if ($target - $val1 >= $val2 - $target) 
        return $val2; 
    else
        return $val1; 
} 
  
// Driver code 
$arr = array( 1, 2, 4, 5, 6, 6, 8, 9 ); 
$n = sizeof($arr); 
$target = 11; 
echo (findClosest($arr, $n, $target)); 
  
// This code is contributed bu Sachin.
?>

输出：

9