Negative numbers in the arrays

JavaScript
1

Tell us what’s happening:
Im working on this challenge of selecting the largest number in a set of arrays, but Im facing the problem of negative numbers. it does not read them.

Your code so far
function largestOfFour(arr){
var largestArray = ;
for(var i = 0; i<arr.length; i++){
var largestNumber = 0;
for(var j = 0; j<arr.length; j++){
if(largestNumber < arr[i][j]){
largestNumber = arr[i][j];
}
}
largestArray.push(largestNumber);
}
return largestArray;
}


function largestOfFour(arr){
var largestArray = [];
for(var i = 0; i<arr.length; i++){
   var largestNumber = 0;
   for(var j = 0; j<arr.length; j++){
      if(largestNumber < arr[i][j]){
         largestNumber = arr[i][j];
      }
   }
   largestArray.push(largestNumber);
}
return largestArray;
}

largestOfFour([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]);

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36.

Challenge: Return Largest Numbers in Arrays

Link to the challenge:

2

Your initial guess of the max value is too big.

 var largestNumber = 0;

You should try a better initial guess, maybe a value that you know is in the array?

1 Like
3

I just initialize it to 1, and the array containing only negative number return 1, I think the solution is to make sure that the value you initiate involves all the numbers,

4

Right. The problem is that this value

 var largestNumber = 0;

could be larger than anything in your array. You don’t want to use a fixed value as your initial guess. You should use the array to help you out.

5

Great, how can I use a dynamic guess?. because there is no need of every time setting that value, it far better have a universal guess that can deal with positive and negative number at the same time.

6

If I have a bag of slips of paper with numbers on them and I’m told to find the biggest number, the first thing I will do is pull out a slip and read the number. That number would be a good guess for the largest number in the bag.

7

Yeah, I got it, I feel it would be better to have a guess which can represent all the numbers!. Anyway thanks!.

8

There is no single number that would work because you can always find an array of numbers that has values smaller than whatever number you guess : )

9

Hi! This one stumped me for a bit, too, but I think I’ve got a solution for you!

Like others have said, you’re automatically disallowing negative numbers from the array by assigning 0 to var largestNumber. Instead of assigning it a value of 0 or declaring it as a new Number (which also doesn’t work), instead try using:
Number.NEGATIVE_INFINITY;

This will effectively allow your code to accept any number, positive or negative, and compare their values appropriately.

Read more about it here: https://devdocs.io/javascript/global_objects/number/negative_infinity

P.S. While this does work, there is another, cleaner solution by studying the arrays. So for anyone else who needs help, I would try for that.

1 Like
10

That will work, but I’m not super enthusiastic about that solution.

let largestNumber = arr[i][0];
for (let j = 1; j < arr[i].length; j++)
  largestNumber = Math.max(largestNumber, arr[i][j]);

This is so much cleaner to me.

1 Like
11

This work exactly as I wanted it to work!. Thanks!.

1 Like