Return Largest Numbers in Arrays using two for loops and getting least negative number

JavaScript
1

Hello I am stumped. I can not seem to figure out how to get the largest number from a sub array, when the sub array is made up of negative numbers. Can any one explain how to do that using for loops? Spoiler below if you haven’t finished this challenge.

  var largestNum=[0,0,0,0]
  
  
  for(let i= 0;i<arr.length;i++){
    for(let j = 0;j<arr[i].length;j++){
if(arr[i][j]>largestNum[i]){
  largestNum[i]=arr[i][j]
}
    }
  }
  return largestNum;
}

largestOfFour([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]); ```
2

As you have notice the initial largest number can’t be 0, if values in array are negative. Consider what else can be used instead of 0 for that.

3

I attempted including an empty array but that didn’t work either.

4

There are at least two approaches

  • What value would be certainly smaller (or equal) than any possible value in array? Small hint could be to think about it from a math perspective.
  • Another possibility is to consider as temporary largest one of the values from array.
5

-infinity ? Is there a way to make the array filled with -infinity in javascript?

6

The project requires you to “RETURN the largest number” in a group of 2nd level arrays but not necessarily return “largestNum” number.

You have to “push” your largest number in a new array.

7

I was having trouble comparing values to the negative numbers in the array, In the top of the code I create an array of zeros, problem is when it compares negative numbers it does not assign a value to the last index.

8

Indeed there’s a way to use infinity concept in javascript. It can be accessed as Infinity or -Infinity

More about it can be read at Infinity - JavaScript | MDN

9

Thanks Sanity! you really helped me understand how to solve my problem! :smiley:


  var largestNum=[-Infinity,-Infinity,-Infinity,-Infinity]
  
  
  for(let i= 0;i<arr.length;i++){
    for(let j = 0;j<arr[i].length;j++){
if(arr[i][j]>largestNum[i]){
  largestNum[i]=arr[i][j]
}
    }
  }
  return largestNum;

}

largestOfFour([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]);
10

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