Basic Algorithm Scripting - Return Largest Numbers in Arrays

[kwame.arms]

Tell us what’s happening:
Trying to work through this challenge. It’s a tough one, but I’m getting better. As it stands my loop is going through each part of the arrays one by one and comparing to see which is greater.

A variable “largest” is compared to the current iteration of the array, if the variable is larger it gets pushed to a new array. If the variable is less than the item in the array, the variable “largest” is then set to that amount.

There are several areas I’m getting hung up on. One is where , for example, 5 gets compared to 1. My if statement will return both true and false. 5 will get pushed to the new array AND 1 will be updated to the largest number. I’ve added plenty of plain text print outs to see what is going on during the code.

This confuses me. Without giving me the solution can anyone give me a hint as to what I’m not able to see.

Your code so far

function largestOfFour(arr) {
var largest = arr[0][0];
var largestArr = [];
console.log(`declaration: largest = ${largest}\n`)

  for (let n = 0; n < arr.length; n++)
  {
    largest = arr[n][0]
    console.log(`Outer loop start, current array items: ${arr[n]}\nlargest is set to first item = ${largest}\n............................................`)
    for (let m = 0; m < arr[n].length; m++)
    {
      if (largest > arr[n][m])
      {
        largestArr.push(largest)
        console.log(`current largest bigger than array item.\nPushed largest to new largestArr: ${largest}\n............................................`)
      }
      largest = arr[n][m]
      console.log(`Current largest, not bigger than array item.\nNew largest: ${largest}\n............................................`)
    }
    
    console.log(`Outer loop end: largestArr items: ${largestArr}`)
  }

  arr = largestArr;
  return arr;
}

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

function largestOfFour(arr) {
var largest = arr[0][0];
var largestArr = [];
console.log(`declaration: largest = ${largest}\n`)

  for (let n = 0; n < arr.length; n++)
  {
    largest = arr[n][0]
    console.log(`Outer loop start, current array items: ${arr[n]}\nlargest is set to first item = ${largest}\n............................................`)
    for (let m = 0; m < arr[n].length; m++)
    {
      if (largest > arr[n][m])
      {
        largestArr.push(largest)
        console.log(`current largest bigger than array item.\nPushed largest to new largestArr: ${largest}\n............................................`)
      }
      largest = arr[n][m]
      console.log(`Current largest, not bigger than array item.\nNew largest: ${largest}\n............................................`)
    }
    
    console.log(`Outer loop end: largestArr items: ${largestArr}`)
  }

  arr = largestArr;
  return arr;
}

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

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Challenge: Basic Algorithm Scripting - Return Largest Numbers in Arrays

Link to the challenge:

freeCodeCamp.org

[hbar1st]

@kwame.arms

var largest = arr[0][0];
var largestArr = [];
console.log(`declaration: largest = ${largest}\n`)

  for (let n = 0; n < arr.length; n++)
  {
    largest = arr[n][0]

At this point in the code in the first loop, you already have a largest (the first number of the first array).

Why do you set it here again?
Shouldn’t you wait till a new larger value is found?

[kwame.arms]

I think the wrong code got put into the post, let me update it

[JeremyLT]

@kwame.arms

  for (let n = 0; n < arr.length; n++)
  {
    for (let m = 0; m < arr[n].length; m++)
    {
      if (largest < arr[n][m])
      {
        largestArr = arr[n];
      }
    }
  }

I would put the reset of ‘largest’ back.

Your problem with the last version is that your push was not in a good location.

Side note - it is very confusing to hold a conversation if you go back and modify the original post.

[hbar1st]

@kwame.arms

    for (let m = 0; m < arr[n].length; m++)
    {
      if (largest < arr[n][m])
      {
        largestArr = arr[n];
      }
    }

Your code finds the first number larger than the first one and assumes it is largest of all (because you immediately store it in the array).

Instead you should just assume it is the largest for now.

Only when you know you have seen all the numbers in this array should you update the largestArr

[kwame.arms]

Yeah, I think I really destroyed this post. I had great intentions but now it’s rubbish.
When I posted originally there were two places where my code was displayed, which could have been confusing. So I edited to remove one.

Wish I could go back to the original post because now somehow my code got overwritten on fCC. The code with all the plain text print outs is lost.

[kwame.arms]

This is all screwed up now, I’m going to scrap it and try again tomorrow.
I’ll heed your advice about editing the OP @JeremyLT

Thanks for all the help/assistance/advice
@hbar1st

[hbar1st]

i have reverted your post (as you wished) to the first version you made originally.

Hope this helps…

[kwame.arms]

I caved and looked at the hints. The closest to my thought process was Hint 1. I see the where I was going wrong, I was using the if statement incorrectly. Also, I was pushing the largest variable into the return array too early.

It’s all part of the process of learning.

[JeremyLT]

I strongly recommend asking more questions instead of looking up the answers. The answer is not the point. Practicing writing code is the point.