Challenge: Get Closest Number in an Array

Given an array of numbers nums, and a given number given_num:

nums = [100, 200, 400, 800, 1600, 3200, 6400, 128000]
given_num = 900

Get the number closest to the given_num from the array nums.

In this example, the returned value should be 800.

Go!

Comments

[Andy Zhao (he/him)]

Ruby:

nums.min_by { |num| (given_num - num).abs }
#=> 800

Shamelessly taken from Stack Overflow 🙃 I was in a much more of a "just give me the answer" mood than "let's figure it out" mood.

[Dian Fay]

Window functions!

SELECT unnest
FROM unnest(ARRAY[100,200,400,800,1600,3200,6400,128000])
ORDER BY row_number() OVER (ORDER BY abs(900 - unnest))
LIMIT 1;

[rhymes]

hahaha thinking outside the box :D

[Dian Fay]

I looked at it again just now and the row_number is redundant anyway...

SELECT unnest
FROM unnest(ARRAY[100,200,400,800,1600,3200,6400,128000])
ORDER BY abs(900 - unnest)
LIMIT 1;

[Maegan Wilson]

I probably over complicated it, but here's a CodePen link with how I did it in JS and outputted it to the HTML side.

[Andy Zhao (he/him)]

Long as you solved it! 👍

[Harshit]

Java:

        int[] nums = {100, 200, 400, 800, 1600, 3200, 6400, 128000};
        int ans = 0;
        int given_num = 900;
        int minDistance = Integer.MAX_VALUE;
        for (int i =0; i < nums.length; i++) {
            int curDistance = Math.abs(nums[i] - given_num);
            if (curDistance < minDistance) {
                ans = nums[i];
                minDistance = curDistance;
            }
        }
        System.out.println(ans);

Trying to optimize no of lines with Java 8 Streams and Lambda.

[Andrey Vladikin]

JS:

const nums = [100, 200, 400, 800, 1600, 3200, 6400, 128000];
const givenNum = 900;

nums
.map(n => ({n, d: Math.abs(n-givenNum)}))
.sort((n1, n2) => Math.sign(n1.d - n2.d))[0].n

[kip]

Rust 🦀

numbers.iter().min_by_key(|&num| (num - given_num).abs()).unwrap()

[Andy Zhao (he/him)]

Nice, didn't know Rust had similar syntax to Ruby!

[Vicente G. Reyes]

With the help of google, I was able to find the answer to this 😅

import numpy as np
def find_nearest(array, value):
array = np.array(array)
z=np.abs(array-value)
y= np.where(z == z.min())
m=np.array(y)
x=m[0,0]
y=m[1,0]
near_value=array[x,y]

return near_value

array =np.array([[100, 200, 400, 800, 1600, 3200, 6400, 128000]])
print(array)
value = 900
print(find_nearest(array, value))

Answer:

Thanks for this challenge! 🍺

[Mikhail Korolev]

Wolfram Language!

Nearest[nums, given_num]

I knew that one day my subscription will come in handy...

[JavaScript Joel]

This is a job for Reduce!

JavaScript:

const nums = [100, 200, 400, 800, 1600, 3200, 6400, 128000]
const given_num = 900

const closestReducer = g => (a, b) =>
  Math.abs(g - a) < Math.abs(g - b) ? a : b

nums.reduce(closestReducer(given_num))
//=> 800

[Pierre Bouillon]

Here goes Python !

min(nums, key=lambda x: abs(x - given_num))

[Andrew Bone]

Javascript:

Let's go for a JS one liner 😉

nums.sort((a, b) => Math.abs(given_num - a) - Math.abs(given_num - b))[0]

This causes the original array to have its order changed but I don't think that's against the rules 😅

[bugb]

I dont think use sort is good idea:
Let see:

[2,3,4,11].sort()

[Andrew Bone]

By including a function to sort by I'm no longer doing an alphabetical sort, which means this problem no longer exists.

  console.log([2,3,4,11].sort((a,b)=>a-b));

Output:
  (4) [2, 3, 4, 11]

The sort() method sorts the elements of an array in place and returns the array. The default sort order is built upon converting the elements into strings, then comparing their sequences of UTF-16 code units values.

developer.mozilla.org/en-US/docs/W...

[bugb]

yes, by including compareFunction callback, we can solve this problem.

[Andy Zhao (he/him)]

If it outputs the closest number, it works! :)

[bugb]

nums = [100, 200, 400, 800, 1600, 3200, 6400, 128000];
given_num = 900

Here is my solution:

f = a => (m=Math.min(...nums.map(v=>Math.abs(v-given_num))),nums.find(v=>v==given_num - m || v== m-given_num))

Usage:

f(nums)

Result:

800

[Gabriel Wu]

Be careful that ... can cause a range error:

RangeError: Maximum call stack size exceeded

when the nums array is very large.

[Dmitry Yakimenko]

C++, O(n), no sorting, no extra memory allocation beyond storing the input:

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    vector<int> v{100, 200, 400, 800, 1600, 3200, 6400, 128000};
    int given_num = 900;

    cout << *min_element(
        v.begin(), 
        v.end(), 
        [=](int a, int b){ return abs(a - given_num) < abs(b - given_num); }
    );

    return 0;
}

[Modaf]

OCaml with list instead of array

let rec closest num list = match list with
[] -> failwith "Empty list"
|[n] -> n
|h :: q ->
    let closest_q = closest num q in
    let val_h = abs (num - h) in
    let val_q = abs (num - closest_q) in
    if (val_h < val_q) then h else closest_q;;

[James Hickey]

Here's some C# for everyone:

var nums = new int[] { 100, 200, 400, 800, 1600, 3200, 6400, 128000 };
var given_num = 900;

var result = 
    (
        from num in nums
        let diff = Math.Abs(given_num - num)
        orderby diff
        select num
    )
    .First();